Add yamllint GitHub workflow

Follow up rubocop/rubocop#10392.

Author: koic

.github/workflows/linting.yml

@@ -0,0 +1,15 @@
+name: Linting
+on:
+  - pull_request
+jobs:
+  yamllint:
+    name: Yamllint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Yamllint
+        uses: karancode/yamllint-github-action@master
+        with:
+          yamllint_comment: true
+        env:
+          GITHUB_ACCESS_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.rubocop.yml

@@ -53,13 +53,13 @@ Layout/ClassStructure:
       - prepend
       - extend
   ExpectedOrder:
-      - module_inclusion
-      - constants
-      - public_class_methods
-      - initializer
-      - instance_methods
-      - protected_methods
-      - private_methods
+    - module_inclusion
+    - constants
+    - public_class_methods
+    - initializer
+    - instance_methods
+    - protected_methods
+    - private_methods
 
 # Trailing white space is meaningful in code examples
 Layout/TrailingWhitespace:

.yamllint.yml

@@ -0,0 +1,9 @@
+extends: default
+
+rules:
+  comments:
+    min-spaces-from-content: 1
+  document-start: disable
+  line-length: disable
+  truthy:
+    check-keys: false

mkdocs.yml

@@ -4,10 +4,10 @@ edit_uri: edit/master/legacy-docs
 copyright: "Copyright © 2012-2022 Bozhidar Batsov and RuboCop contributors"
 docs_dir: legacy-docs
 pages:
-- Home: index.md
-- Installation: installation.md
-- Usage: usage.md
-- Cops: cops.md
-- Cops Documentation:
-    - Performance Cops: cops_performance.md
+  - Home: index.md
+  - Installation: installation.md
+  - Usage: usage.md
+  - Cops: cops.md
+  - Cops Documentation:
+      - Performance Cops: cops_performance.md
 theme: readthedocs