Add PHPCS checks to the scaffold

.github/workflows/php.yml

@@ -0,0 +1,36 @@
+name: PHP Checks
+
+on:
+  push:
+    branches: [ "trunk" ]
+  pull_request:
+    branches: [ "trunk" ]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v3
+
+      - name: Validate composer.json and composer.lock
+        run: composer validate --strict
+
+      - name: Cache Composer packages
+        id: composer-cache
+        uses: actions/cache@v3
+        with:
+          path: vendor
+          key: ${{ runner.os }}-php-${{ hashFiles('**/composer.lock') }}
+          restore-keys: |
+            ${{ runner.os }}-php-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-progress
+
+      - name: Run test suite
+        run: composer lint