- bump dependencies

- added phpstan 8.1 CI steps
- documentation fix

Author: astepin

.github/workflows/ci.yml

@@ -26,18 +26,20 @@ jobs:
     name: PHPStan
 
     runs-on: ubuntu-latest
-
+    strategy:
+      matrix:
+        php-versions: ['7.4', '8.1']
     steps:
       - uses: actions/checkout@v2
       - uses: php-actions/composer@v5
         with:
-          php_version: 7.4
+          php_version: ${{ matrix.php-versions }}
 
       - name: PHPStan Static Analysis
         uses: php-actions/phpstan@v3
         with:
           path: src/
-          php_version: 7.4
+          php_version: ${{ matrix.php-versions }}
 
   build-test:
     runs-on: ubuntu-latest