Added PHP validation via GH actions

Author: SebKay

.github/workflows/php.yml

@@ -0,0 +1,20 @@
+name: Test PHP
+
+on: [pull_request]
+
+jobs:
+  build:
+    name: Test
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - name: Setup Composer Access
+      run: composer config -g github-oauth.github.com ${{ secrets.GH_ACCESS_TOKEN }}
+
+    - name: Install dependencies
+      run: composer install --prefer-dist --no-progress --no-suggest
+
+    - name: Validate code against PSR2
+      run: ./vendor/bin/phpcs ./ --extensions=php --standard=PSR2 --ignore=vendor/