ci: add GitHub Actions workflow

Run PHPUnit, PHPStan, PHPCS, and doc test linting on push and PR to main.

Author: tmihalicka

.github/workflows/ci.yml

@@ -0,0 +1,42 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+jobs:
+  tests:
+    name: PHP ${{ matrix.php }} - ${{ matrix.stability }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        php: ['8.4']
+        stability: [prefer-stable]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php }}
+          extensions: mbstring, intl, bcmath
+          coverage: xdebug
+
+      - name: Install dependencies
+        run: composer update --${{ matrix.stability }} --prefer-dist --no-interaction
+
+      - name: Run PHPUnit
+        run: vendor/bin/phpunit
+
+      - name: Run PHPStan
+        run: vendor/bin/phpstan analyse --no-progress --memory-limit=512M
+
+      - name: Run PHPCS
+        run: vendor/bin/phpcs --standard=phpcs.ruleset.xml src tests
+
+      - name: Run doc tests
+        run: php bin/doctest lint --directory=tests/Fixtures/EndToEnd --no-cache