I have updated [examples/with-markdown](https://github.com/zeit/next.js/tree/canary/examples/with-markdown) in order to make it works with next 6 🎉
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<summary>Error</summary>
Error: Plugin/Preset files are not allowed to export objects, only functions. In /Users/zhenyatelegin/Desktop/next.js/examples/with-markdown/node_modules/markdown-in-js/babel.js
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* Examples: clarify language around Yarn create & npx
* add missing READMEs and create-next-app usage
* suggest people tag jthegedus in firebase related issues
* add yarn alt instructions
* cerebraljs example readme & fixes
* 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