Add code style check to CI

Author: matthiasnoback

.github/workflows/code-style.yaml

@@ -0,0 +1,35 @@
+name: Code style
+
+on:
+  pull_request: null
+  push:
+    branches:
+      - master
+
+jobs:
+  code_analysis:
+    strategy:
+      fail-fast: false
+      matrix:
+        actions:
+          -
+            name: "Code style"
+            run: vendor/bin/php-cs-fixer fix -v --diff --dry-run
+        php-versions: ['7.4']
+
+    name: ${{ matrix.actions.name }}
+    runs-on: ubuntu-latest
+
+    steps:
+      -   uses: actions/checkout@v2
+
+      # see https://github.com/shivammathur/setup-php
+      -   uses: shivammathur/setup-php@v2
+          with:
+            php-version: ${{ matrix.php-versions }}
+            coverage: none
+
+      # composer install cache - https://github.com/ramsey/composer-install
+      -   uses: "ramsey/composer-install@v1"
+
+      -   run: ${{ matrix.actions.run }}