migrates to GitHub workflows

.github/workflows/CI.yml

@@ -0,0 +1,48 @@
+name: CI
+
+on: [push]
+
+jobs:
+  build:
+    runs-on: ${{ matrix.operating-system }}
+    strategy:
+      matrix:
+        operating-system: [ubuntu-latest]
+        php-versions: ["7.2", "7.3", "7.4", 8.0"]
+    env:
+      tools: composer
+    name: PHP ${{ matrix.php-versions }} test on ${{ matrix.operating-system }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          tools: ${{ env.tools }}
+        env:
+          fail-fast: true
+
+      - name: Setup problem matchers for PHPUnit
+        run: echo "::add-matcher::${{ runner.tool_cache }}/phpunit.json"
+
+      - name: Validate composer
+        run: composer validate
+
+      - 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
+
+      - name: Run tests
+        run: composer test