Add CI

.github/workflows/ci.yaml

@@ -0,0 +1,51 @@
+name: CI
+on:
+  - push
+  - pull_request
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        php-version:
+          - "7.4"
+          - "8.0"
+
+    name: PHP ${{ matrix.php-version }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup PHP, with composer and extensions
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-version }}
+          tools: phpstan
+
+      - name: Setup problem matchers for PHP
+        run: echo "::add-matcher::${{ runner.tool_cache }}/php.json"
+
+      - name: Setup problem matchers for PHPUnit
+        run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
+
+
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "::set-output name=dir::$(composer config cache-files-dir)"
+
+      - name: Cache dependencies
+        uses: actions/cache@v2
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+
+      - name: Install dependencies
+        run: composer install --prefer-dist
+
+      - name: Test with PHPUnit
+        run: ./vendor/bin/phpunit
+
+      - name: Run PHPStan
+        run: phpstan analyse src