* remove global npm install of create-next-app
* add npx to create-next-app command in examples
* add bash to shell snippets
* add yarn create to next-app command in examples
* fix READMEs named with lowercase
* change READMEs to use UPPERCASE
* #3700 Add examples for next-sass
* #3700 Use React.Fragments and more
* Fix#3700 remove some keys to make more clear
* Fix#3700, change to without-css-modules
* Replace PageWrapper with _document for more concise code. #3700