Add GH Action for CI tests

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: CI Tests
+on: [push, pull_request]
+
+jobs:
+  PHPUnit:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os:
+          - ubuntu-latest
+        php:
+          - 8.2
+          - 8.3
+          - 8.4
+
+    steps:
+      - uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+
+      - name: Install dependencies
+        run: composer install
+
+      - name: Run PHPUnit
+        run: vendor/bin/phpunit