Add code coverage generation

.github/workflows/coverage.yml

@@ -0,0 +1,23 @@
+name: PHPStan
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+
+jobs:
+  phpstan:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+      - name: Install dependencies
+        run: composer install
+      - name: "Run test suite"
+        run: vendor/bin/phpunit --coverage-clover=coverage.xml
+      - name: Upload coverage to Codecov
+        uses: codecov/codecov-action@v3
+        with:
+          file: ./coverage.xml
+          fail_ci_if_error: true

.gitignore

@@ -7,6 +7,7 @@ composer.lock
 
 # PHPUnit
 .phpunit.result.cache
+coverage.xml
 
 # JetBrains
 .idea