refactor: rename Git master branch to main (#5345)

* Prepare to renaming master branch to main

* Update CONTRIBUTING.md

* Update packages/docusaurus-migrate/src/__tests__/__fixtures__/missing_version_website/website/package.json

* Update packages/docusaurus-migrate/src/__tests__/__fixtures__/complex_website/website/package.json

* Update packages/docusaurus-migrate/src/__tests__/__fixtures__/simple_website/website/package.json

* missing master -> main replaces

* useless char

* For GH Pages org deploy, DEPLOYMENT_BRANCH env is now required

* fix versioning page

* fix vercel links

* update deployment.mdx

Co-authored-by: Sébastien Lorber <slorber@users.noreply.github.com>
Co-authored-by: slorber <lorber.sebastien@gmail.com>

docusaurus.config.js

@@ -91,14 +91,13 @@ module.exports = {
         docs: {
           sidebarPath: require.resolve('./sidebars.js'),
           // Please change this to your repo.
-          editUrl:
-            'https://github.com/facebook/docusaurus/edit/master/website/',
+          editUrl: 'https://github.com/facebook/docusaurus/edit/main/website/',
         },
         blog: {
           showReadingTime: true,
           // Please change this to your repo.
           editUrl:
-            'https://github.com/facebook/docusaurus/edit/master/website/blog/',
+            'https://github.com/facebook/docusaurus/edit/main/website/blog/',
         },
         theme: {
           customCss: require.resolve('./src/css/custom.css'),