**What's this PR?**
Based on the feedback on [this PR](https://github.com/zeit/next.js/pull/5722) @timneutkens asked me to create a test for `ssr: true`
**What's it do?**
- adds a test for setting `ssr: true` - /basic
- adds a test for setting `ssr: true` - /production
* Layout ground works for next/async
* Implement the Dynamic Bundle feature.
* Add some test cases.
* Update README.
* Implement props aware dynamic bundle API.
* Update tests and README.
* Add a test case for React Context support.
* Always check with the fs when gettings chunks.
* Add a new set of test cases for dynamic imports in dev.
* Add dynamic import test cases for production.
* Add availableChunks support for static exports.