Issue #14: Add github action to run tests.

.github/workflows/ci.yaml

@@ -0,0 +1,28 @@
+name: CI Packages
+
+on:
+  - push
+
+jobs:
+  tests:
+    name: Tests
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: true
+      matrix:
+        php: [7.4]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          # @todo Review which extensions are needed.
+          extensions: dom, curl, libxml, mbstring, zip, pcntl, pdo, sqlite, pdo_sqlite, gd
+          coverage: none
+
+      - run: composer install --no-interaction
+
+      - run: vendor/bin/phpunit