Test PHP Composer runner of GitHub

GitHub has these new CI/CD features, so let's test whether this makes sense.

I guess this PHP thing just installs the project via composer… :thinking:

.github/workflows/php.yml

@@ -0,0 +1,23 @@
+name: PHP Composer
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v1
+
+    - name: Validate composer.json and composer.lock
+      run: composer validate
+
+    - name: Install dependencies
+      run: composer install --prefer-dist --no-progress --no-suggest
+
+    # Add a test script to composer.json, for instance: "test": "vendor/bin/phpunit"
+    # Docs: https://getcomposer.org/doc/articles/scripts.md
+
+    # - name: Run test suite
+    #   run: composer run-script test