Migrate from "master" branch to "main" (#11715)

* Remove dead link

* Use consistent "homepage" url in package.json

* Update md links

* Update comment link in parser d.ts

* Add comment in gitpod config

* Update circleci config

* Update PULL_REQUEST_TEMPLATE

* Update badges

* Trigger CI

* Update 404 link

packages/babel-parser/typings/babel-parser.d.ts

@@ -1,5 +1,5 @@
 // Type definitions for @babel/parser
-// Project: https://github.com/babel/babel/tree/master/packages/babel-parser
+// Project: https://github.com/babel/babel/tree/main/packages/babel-parser
 // Definitions by: Troy Gerwien <https://github.com/yortus>
 //                 Marvin Hagemeister <https://github.com/marvinhagemeister>
 //                 Avi Vahl <https://github.com/AviVahl>