Main branch cleanup (flutter#7855)

Author: mit-mit

CONTRIBUTING.md

@@ -15,7 +15,7 @@ To contribute a fix to a repo, submit a [pull request
 
 For information on contributing code or API docs to the Flutter SDK, see
 [Contributing to
-Flutter](https://github.com/flutter/flutter/blob/master/CONTRIBUTING.md)
+Flutter](https://github.com/flutter/flutter/blob/main/CONTRIBUTING.md)
 in the [Flutter SDK](https://github.com/flutter/flutter) repo.
 
 We are also happy to accept your PRs to the

README.md

@@ -9,7 +9,7 @@
 
 [Build Status]: https://github.com/flutter/website/workflows/build/badge.svg
 [Flutter]: https://docs.flutter.dev/
-[Repo on GitHub Actions]: https://github.com/flutter/website/actions?query=workflow%3Abuild+branch%3Amaster
+[Repo on GitHub Actions]: https://github.com/flutter/website/actions?query=workflow%3Abuild+branch%3Amain
 
 ## Table of contents
 

example/README.md

@@ -1,4 +1,4 @@
-Code snippets extracted using [tool/extract.dart](https://github.com/flutter/website/blob/master/tool/extract.dart), are saved
+Code snippets extracted using [tool/extract.dart](https://github.com/flutter/website/blob/main/tool/extract.dart), are saved
 into [example.g](example.g). The Yaml files in this folder are copied into
 [example.g](example.g), then the snippets are run through the analyzer and
 formatter.

firebase.json

@@ -137,7 +137,7 @@
       { "source": "/testing/ui-performance", "destination": "/perf/ui-performance", "type": 301 },
       { "source": "/whats-new-archive", "destination": "/whats-new", "type": 301 },
 
-      { "source": "/assets/images/docs/intellij/hot-reload.gif", "destination": "https://raw.githubusercontent.com/flutter/website/master/src/assets/images/docs/tools/android-studio/hot-reload.gif", "type": 301 },
+      { "source": "/assets/images/docs/intellij/hot-reload.gif", "destination": "https://raw.githubusercontent.com/flutter/website/main/src/assets/images/docs/tools/android-studio/hot-reload.gif", "type": 301 },
       { "source": "/catalog/samples", "destination": "https://flutter.github.io/samples/#", "type": 301 },
       { "source": "/catalog/samples", "destination": "https://flutter.github.io/samples/#", "type": 301 },
       { "source": "/catalog/samples/*", "destination": "https://flutter.github.io/samples/#", "type": 301 },
@@ -180,7 +180,6 @@
       { "source": "/go/base-annotations-local-position-on-region", "destination": "https://docs.google.com/document/d/1r7FQTOw2vZJZ5c0VoNqi9CWmZY3MvUfz0spdf0-nK6k/edit", "type": 301 },
       { "source": "/go/blankcanvas", "destination": "https://docs.google.com/document/d/1rS_RO2DQ_d4_roc3taAB6vXFjv7-9hJP7pyZ9NhPOdA/edit?resourcekey=0-VBzTPoqLwsruo0j9dokuOg", "type": 301 },
       { "source": "/go/bottom-navigation-bar-title-deprecation", "destination": "https://docs.google.com/document/d/1L-2nPf5hbLGNoRvOSUmnxgUHahBVzW1ybhTXGY3ObDw/edit?usp=sharing", "type": 301 },
-      { "source": "/go/breaking-changes-template", "destination": "https://github.com/flutter/website/blob/master/src/docs/release/breaking-changes/template.md", "type": 301 },
       { "source": "/go/buffer-queue", "destination": "https://docs.google.com/document/d/1rXl9G-VmISVlVkKVgrnQKeX7Mexyez0x9HZ5F5yKxrQ/edit?usp=sharing", "type": 301 },
       { "source": "/go/build-aar", "destination": "/development/add-to-app/android/project-setup#option-a---depend-on-the-android-archive-aar", "type": 301 },
       { "source": "/go/build-dashboard-v2", "destination": "https://docs.google.com/document/d/1kwh48xYuoVtadYFb2I2t6BJMGEW07K7T5WYcieAZZiY", "type": 301 },