Adding code coverage

Author: moufmouf

.travis.yml

@@ -53,3 +53,6 @@ script:
   #- ./vendor/bin/simple-phpunit $PHPUNIT_FLAGS
   - composer phpstan
   - ./vendor/bin/phpunit
+
+after_success:
+  - travis_retry php vendor/bin/php-coveralls -v

composer.json

@@ -27,7 +27,8 @@
     "symfony/security-bundle": "^4.1.9",
     "symfony/yaml": "^4.1.9",
     "phpunit/phpunit": "^8.0.4",
-    "phpstan/phpstan": "^0.11.4"
+    "phpstan/phpstan": "^0.11.4",
+    "php-coveralls/php-coveralls": "^2.1"
   },
   "scripts": {
     "phpstan": "phpstan analyse TdbmGraphqlBundle.php DependencyInjection/ Resources/ -c phpstan.neon --level=7 --no-progress"