Add github actions test workflow

.github/workflows/tests.yml

@@ -0,0 +1,45 @@
+name: Tests
+
+on:
+  push:
+  pull_request:
+  schedule:
+    - cron: '0 0 * * *'
+
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php:
+          - 5.3
+          - 5.4
+          - 5.5
+          - 5.6
+          - 7.0
+          - 7.1
+          - 7.2
+          - 7.3
+          - 7.4
+
+    name: PHP ${{ matrix.php }}
+
+    steps:
+      - name: Check out code
+        uses: actions/checkout@v4
+        with:
+          submodules: true
+
+      - name: Install PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          coverage: none
+
+      - name: Install dependencies
+        run: composer install --prefer-dist --no-interaction --no-progress
+
+      - name: Run tests
+        run: vendor/bin/phpunit