lint & example fixes (#3160)

* fix import extensions of eslint

* revert next.config.cjs

* fix eslint globbing

* add migrating to docs’ sidebar

* fix prettier error on Contributing.md

* put quotes for glob matching for windows user

* remove type: module from  package.json

packages/slate-react/package.json

@@ -1,6 +1,5 @@
 {
   "name": "slate-react",
-  "type": "module",
   "description": "Tools for building completely customizable rich-text editors with React.",
   "version": "0.50.1",
   "license": "MIT",