Add php-cs check action

Signed-off-by: Christoph Wurst <christoph@winzerhof-wurst.at>

.github/workflows/lint.yml

@@ -18,3 +18,19 @@ jobs:
         coverage: none
     - name: Lint
       run: composer run lint
+
+  php-cs-fixer:
+    name: php-cs check
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout
+      uses: actions/checkout@master
+    - name: Set up php
+      uses: shivammathur/setup-php@master
+      with:
+        php-version: 7.4
+        coverage: none
+    - name: Install dependencies
+      run: composer i
+    - name: Run coding standards check
+      run: composer run cs:check