Rename "master" to "main"

.github/workflows/ci.yml

@@ -4,7 +4,7 @@ on:
   pull_request:
   push:
     branches:
-    - master
+    - main
   schedule:
   - cron: '0 1 * * *'
 

.github/workflows/publish-docs.yml

@@ -8,7 +8,7 @@ on:
     inputs:
       ref:
         description: 'Git revision'
-        default: 'master'
+        default: 'main'
         required: true
 
 jobs:

README.md

@@ -17,6 +17,6 @@ For more info on Maud,
 see the [official book][book].
 
 [book]: https://maud.lambda.xyz/
-[booksrc]: https://github.com/lambda-fairy/maud/tree/master/docs
+[booksrc]: https://github.com/lambda-fairy/maud/tree/main/docs
 [apiref]: https://docs.rs/maud/
-[changelog]: https://github.com/lambda-fairy/maud/blob/master/CHANGELOG.md
+[changelog]: https://github.com/lambda-fairy/maud/blob/main/CHANGELOG.md