ci: add GHA

.github/workflows/ci.yaml

@@ -0,0 +1,60 @@
+name: CI
+
+on:
+    push:
+        branches: [ main ]
+    pull_request: ~
+
+jobs:
+    cs:
+        name: Coding Standards
+        runs-on: ubuntu-latest
+        steps:
+            - name: Checkout
+              uses: actions/checkout@v3
+
+            - name: PHP-CS-Fixer
+              uses: docker://oskarstark/php-cs-fixer-ga
+              with:
+                args: --diff --dry-run
+
+    phpstan:
+        name: PHPStan
+        runs-on: ubuntu-latest
+        steps:
+            - name: Checkout
+              uses: actions/checkout@v3
+
+            - name: PHP-CS-Fixer
+              uses: docker://oskarstark/phpstan-ga
+
+    phpunit:
+        name: PHPUnit on PHP ${{ matrix.php-version }} ${{ matrix.name }}
+        runs-on: ubuntu-latest
+        strategy:
+            fail-fast: false
+            matrix:
+                php-version: ['8.2', '8.3']
+                composer-flags: ['']
+                name: ['']
+                include:
+                    - php-version: 8.1
+                      composer-flags: '--prefer-lowest'
+                      name: '(prefer lowest dependencies)'
+        steps:
+            - name: Checkout
+              uses: actions/checkout@v3
+
+            - name: Setup PHP, with composer and extensions
+              uses: shivammathur/setup-php@v2
+              with:
+                  php-version: ${{ matrix.php-version }}
+                  extensions: mbstring, xml
+                  ini-values: phar.readonly="Off"
+
+            - name: Install Composer dependencies
+              run: |
+                  composer update --prefer-dist --no-interaction ${{ matrix.composer-flags }}
+
+            - name: Run Tests
+              run: vendor/bin/simple-phpunit