Update/fix "examples/with-firebase-hosting-and-typescript" (#5864)

There were several issues with the example [examples/with-firebase-hosting-and-typescript](https://github.com/zeit/next.js/tree/canary/examples/with-firebase-hosting-and-typescript)
* `npm run serve`
  * Has no `pre` task that actually builds the app. Requires manual running of all build scripts.
  * Will choke on windows because trying to set environment variables with `NODE_ENV=production`
* Outdated Typescript and Tslint
* Not being able to deploy because `firebase-tools` being of a deprecated version.
* Structure, which I understand is based on `firebase-tools` generation, is confising with `src/functions/src` being generally bad structuring.

I remedied this and also improved some other factors:

* Remove dependency `prettier` as it is unused (f4d6f54)
* Upgrade all dependencies (09a9193)
  * Use upgraded firebase dependencies to deploy to node 8 environment (87e1e09, 7d8055b)
  * Remove deprecated tslint rule `no-unused-variable` (9392162)
* Flattened filestructure in `src/functions` (097a25a)
* Use ES import when importing next (6c99adb)
* Fixed incorrect name and added somewhat to the description in package.json.
  `with-firebase-hosting` → `with-firebase-hosting-and-typescript` (1ffa0b5)
* Fixed `serve` script by building before running, using [`cross-env`](https://www.npmjs.com/package/cross-env) to set environment variables and remove unecessary flag. (3a1e221, 422ccee, 8811e44)
* Add `.firebase` cache to `.gitignore` (4d7cbe4)
* Add `-C` (clean) flag when copying dependency files `copy-deps` (0826708)
* Use `strict: true` in the functions tsconfig (229b04f)

This was tested by running serve on windows and linx(WSL) and deploy on linux(WSL)

---

This is based on #5819 but correctly based from `canary`

examples/with-firebase-hosting-and-typescript/.gitignore

@@ -1 +1,4 @@
 dist/
+
+# Firebase cache
+.firebase/

examples/with-firebase-hosting-and-typescript/README.md

@@ -72,3 +72,7 @@ If you're having issues, feel free to tag @sampsonjoliver in the [issue you crea
 * The empty `placeholder.html` file is so Firebase Hosting does not error on an empty `public/` folder and still hosts at the Firebase project URL.
 * `firebase.json` outlines the catchall rewrite rule for our Cloud Function.
 * The [Firebase predeploy](https://firebase.google.com/docs/cli/#predeploy_and_postdeploy_hooks) hooks defined in `firebase.json` will handle linting and compiling of the next app and the functions sourceswhen `firebase deploy` is invoked. The only scripts you should need are `dev`, `clean` and `deploy`.
+* Specifying [`"engines": {"node": "8"}`](package.json#L5-L7) in the `package.json` is required for firebase functions
+  to be deployed on Node 8 rather than Node 6
+  ([Firebase Blog Announcement](https://firebase.googleblog.com/2018/08/cloud-functions-for-firebase-config-node-8-timeout-memory-region.html))
+  . This is matched in by specifying target as `es2017` in [`src/functions/tsconfig.json`](src/functions/tsconfig) so that typescript output somewhat compacter and moderner code.

examples/with-firebase-hosting-and-typescript/package.json

@@ -1,10 +1,14 @@
 {
-  "name": "with-firebase-hosting",
+  "name": "with-firebase-hosting-and-typescript",
   "version": "1.0.0",
-  "description": "Host Next.js SSR app on Firebase Cloud Functions with Firebase Hosting redirects.",
+  "description": "Host Next.js SSR app on Firebase Cloud Functions with Firebase Hosting redirects. Built with typescript.",
+  "engines": {
+    "node": "8"
+  },
   "scripts": {
     "dev": "next src/app",
-    "serve": "NODE_ENV=production firebase serve --only functions,hosting",
+    "preserve": "npm run build-public && npm run build-functions && npm run build-app && npm run copy-deps && npm run install-deps",
+    "serve": "cross-env NODE_ENV=production firebase serve",
     "deploy": "firebase deploy",
     "clean": "rimraf \"dist/functions\" && rimraf \"dist/public\"",
     "build-app": "next build \"src/app\"",
@@ -13,26 +17,26 @@
     "lint-app": "tslint --project src/app",
     "typecheck-app": "tsc --project src/app",
     "lint-functions": "tslint --project src/functions",
-    "copy-deps": "cpx \"*{package.json,package-lock.json,yarn.lock}\" \"dist/functions\"",
+    "copy-deps": "cpx \"*{package.json,package-lock.json,yarn.lock}\" \"dist/functions\" -C",
     "install-deps": "cd \"dist/functions\" && npm i"
   },
   "dependencies": {
-    "@zeit/next-typescript": "1.1.0",
-    "firebase-admin": "~5.12.1",
-    "firebase-functions": "^1.0.1",
-    "next": "^6.0.3",
-    "react": "^16.3.2",
-    "react-dom": "^16.3.2"
+    "@zeit/next-typescript": "^1.1.0",
+    "firebase-admin": "^6.3.0",
+    "firebase-functions": "^2.1.0",
+    "next": "^7.0.0",
+    "react": "^16.6.0",
+    "react-dom": "^16.6.0"
   },
   "devDependencies": {
-    "@types/next": "^2.4.10",
-    "@types/react": "^16.3.14",
+    "@types/next": "^7.0.0",
+    "@types/react": "^16.6.0",
     "cpx": "1.5.0",
-    "firebase-tools": "3.18.4",
-    "prettier": "1.12.1",
+    "cross-env": "5.2.0",
+    "firebase-tools": "^6.1.0",
     "rimraf": "2.6.2",
-    "tslint": "^5.8.0",
-    "tslint-react": "3.6.0",
-    "typescript": "^2.5.3"
+    "tslint": "^5.11.0",
+    "tslint-react": "^3.6.0",
+    "typescript": "^3.2.0"
   }
 }

examples/with-firebase-hosting-and-typescript/src/functions/index.ts

@@ -1,5 +1,5 @@
 import * as functions from 'firebase-functions';
-const next = require('next');
+import * as next from 'next';
 
 const dev = process.env.NODE_ENV !== 'production';
 const app = next({ dev, conf: { distDir: 'next' } });

examples/with-firebase-hosting-and-typescript/src/functions/src/index.ts

@@ -1,3 +0,0 @@
-import * as functions from 'firebase-functions';
-
-export { nextApp } from './app/next';

examples/with-firebase-hosting-and-typescript/src/functions/tsconfig.json

@@ -1,13 +1,12 @@
 {
   "compilerOptions": {
-    "lib": ["es6"],
+    "lib": ["es2017"],
     "module": "commonjs",
-    "noImplicitReturns": true,
+    "strict": true,
     "outDir": "../../dist/functions",
     "sourceMap": true,
-    "target": "es6",
-    "baseUrl": "./src"
+    "target": "es2017",
+    "baseUrl": "./"
   },
-  "compileOnSave": true,
-  "include": ["src"]
+  "compileOnSave": true
 }

examples/with-firebase-hosting-and-typescript/src/functions/tslint.json

@@ -107,9 +107,6 @@
     // Warns if function overloads could be unified into a single function with optional or rest parameters.
     "unified-signatures": {"severity": "warning"},
 
-    // Warns if code has an import or variable that is unused.
-    "no-unused-variable": {"severity": "warning"},
-
     // Prefer const for values that will not change. This better documents code.
     "prefer-const": {"severity": "warning"},