Add initial GitHub Actions setup

Author: Ayesh

.gitattributes

@@ -0,0 +1,14 @@
+# https://php.watch/articles/composer-gitattributes
+
+# Exclude build/test files from archive
+/.github          export-ignore
+/build            export-ignore
+/tests            export-ignore
+/.gitattributes   export-ignore
+/.gitignore       export-ignore
+/phpunit.xml      export-ignore
+/phpunit.xml.dist export-ignore
+
+# Configure diff output for .php and .phar files.
+*.php diff=php
+*.phar -diff

.github/workflows/ci.yml

@@ -0,0 +1,47 @@
+name: PHPUnit tests
+on: [push, pull_request]
+jobs:
+  phpunit:
+    name: PHPUnit tests
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        php-versions: ['8.2']
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v3
+
+      # Docs: https://github.com/shivammathur/setup-php
+      - name: Setup PHP
+        uses: shivammathur/setup-php@v2
+        with:
+          php-version: ${{ matrix.php-versions }}
+          extensions: curl
+          coverage: xdebug
+
+      - name: Get composer cache directory
+        id: composer-cache
+        run: echo "dir=$(composer config cache-files-dir)" >> $GITHUB_OUTPUT
+
+      - name: Cache composer dependencies
+        uses: actions/cache@v3
+        with:
+          path: ${{ steps.composer-cache.outputs.dir }}
+          # Use composer.json for key, if composer.lock is not committed.
+          # key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
+          key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
+          restore-keys: ${{ runner.os }}-composer-
+
+      - name: Install Composer dependencies
+        run: composer install --no-progress --prefer-dist --optimize-autoloader
+
+      - name: Show version information
+        run: |
+          php -v
+          php -m
+          composer --version
+
+      - name: Test with phpunit
+        run: vendor/bin/phpunit --coverage-text