Add CI badge.

Author: dereuromark

.github/workflows/ci.yml

@@ -58,7 +58,7 @@ jobs:
         tools: pecl
 
     - name: Composer install
-      run: composer update --prefer-stable
+      run: composer update
 
     - name: Run phpcs
       run: vendor/bin/phpcs --version && vendor/bin/phpcs --report=checkstyle