CI: added tests as Github Action

.github/workflows/tests.yml

@@ -0,0 +1,32 @@
+name: Tests
+
+on:
+  - push
+  - pull_request
+
+jobs:
+  tests:
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest, macOS-latest]
+        php: ['7.1', '7.2', '7.3', '7.4', '8.0']
+
+      fail-fast: false
+
+    name: PHP ${{ matrix.php }} tests on ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v2
+      - uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          extensions: tokenizer
+          coverage: none
+
+      - run: composer install --no-progress --prefer-dist
+      - run: vendor/bin/tester tests -s -C
+      - if: failure()
+        uses: actions/upload-artifact@v2
+        with:
+          name: output
+          path: tests/**/output