chore(ci): add github actions CI

.github/workflows/tests.yml

@@ -0,0 +1,38 @@
+name: Tests
+
+on:
+  push:
+  pull_request:
+
+jobs:
+  run:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        php-versions: ['7.3', '7.4', '8.0']
+        composer-stability: [ 'prefer-lowest', 'prefer-stable' ]
+
+    name: PHP ${{ matrix.php }} - ${{ matrix.stability }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          tools: composer:v2
+
+      - name: Validate composer.json
+        run: composer validate
+
+      - name: Install dependencies
+        run: composer update --prefer-source --no-interaction --${{ matrix.stability }}
+
+      - name: Run phpspec tests
+        run: ./bin/phpspec run --format=dot
+
+      - name: Run behat tests
+        run: ./bin/behat