[CI] Add yaml validation

.github/workflows/yaml.yml

@@ -0,0 +1,42 @@
+name: YAML
+
+on:
+  push:
+    paths:
+      - '**.yaml'
+      - '**.yml'
+  pull_request:
+    paths:
+      - '**.yaml'
+      - '**.yml'
+
+jobs:
+  yaml-validation:
+    name: YAML validation
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 1
+      - name: Setup PHP version
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: 7.4
+          extensions: mbstring
+      - name: Get Composer Cache Directory
+        id: composer-cache
+        run: |
+          echo "::set-output name=dir::$(composer config cache-files-dir)"
+      - name: Cache composer dependencies
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
+          restore-keys: ${{ runner.os }}-composer-
+      - name: Install composer dependencies
+        run: |
+          composer update --no-progress --prefer-dist --optimize-autoloader
+      - name: Lint yaml files
+        run: |
+          make yaml-lint

Makefile

@@ -1,5 +1,5 @@
 .PHONY: qa
-qa: coding-standards tests
+qa: coding-standards tests yaml-lint
 
 .PHONY: code-coverage
 code-coverage: vendor
@@ -22,6 +22,10 @@ vendor: composer.json composer.lock
 xlf-lint:
 	xmllint --schema Resources/Private/Language/xliff-core-1.2-strict.xsd --noout Resources/Private/Language/*.xlf
 
+.PHONY: yaml-lint
+yaml-lint: vendor
+	find -regex '.*\.ya?ml' ! -path "./.Build/*" ! -path "./Build/*" -exec .Build/bin/yaml-lint -v {} \;
+
 .PHONY: zip
 zip:
 	grep -Po "(?<='version' => ')([0-9]+\.[0-9]+\.[0-9]+)" ext_emconf.php | xargs -I {version} sh -c 'mkdir -p ../zip; git archive -v -o "../zip/$(shell basename $(CURDIR))_{version}.zip" v{version}'

composer.json

@@ -27,6 +27,7 @@
 		"friendsofphp/php-cs-fixer": "^2.19",
 		"php-coveralls/php-coveralls": "^2.4",
 		"phpunit/phpunit": "^8.5 || ^9.5",
+		"symfony/yaml": "^4.4 || 5.3",
 		"typo3/coding-standards": "^0.3"
 	},
 	"suggest": {