Add github workflow

.github/workflows/php-checks.yml

@@ -0,0 +1,38 @@
+on: [push]
+name: PHP checks
+jobs:
+  composer-check:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        php-versions: ['7.2', '7.3', '7.4']
+    name: PHP ${{ matrix.php-versions }} tests
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          tools: cs2pr
+
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "::set-output name=dir::$(composer config cache-files-dir)"
+
+      - name: Cache dependencies
+        uses: actions/cache@v1
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+
+      - name: Run Composer install
+        run: composer install --prefer-dist
+
+      - name: Run PHP checks
+        run: composer phpcheck
+
+      - name: Run PHPUnit
+        run: composer phpunit