Use checkstyle format for phpstan.

.github/workflows/ci.yml

@@ -214,6 +214,7 @@ jobs:
         php-version: '7.2'
         extensions: mbstring, intl, apcu
         coverage: none
+        tools: cs2pr
 
     - name: Get composer cache directory
       id: composer-cache
@@ -236,4 +237,4 @@ jobs:
       run: vendor/bin/psalm.phar --show-info=false --output-format=github
 
     - name: Run phpstan
-      run: vendor/bin/phpstan.phar analyse --no-progress src/
+      run: vendor/bin/phpstan.phar analyse src/ --error-format=checkstyle | cs2pr