Automatically run PHP CS as github action

Signed-off-by: Joas Schilling <coding@schilljs.com>

.github/workflows/lint.yml

@@ -0,0 +1,45 @@
+name: Lint
+
+on:
+  pull_request:
+  push:
+    branches:
+      - master
+      - stable*
+
+jobs:
+  php:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        php-versions: ['7.2', '7.3', '7.4']
+
+    name: php${{ matrix.php-versions }}
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Set up php ${{ matrix.php-versions }}
+        uses: shivammathur/setup-php@v1
+        with:
+          php-version: ${{ matrix.php-versions }}
+          coverage: none
+
+      - name: Lint
+        run: composer run lint || ( echo 'Please run `composer run lint` and fix your code' && exit 1 )
+
+  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 || ( echo 'Please run `composer run cs:fix` to format your code' && exit 1 )