feat: require slevomat/coding-standard v8.15 (#144)

Author: simPod

composer.json

@@ -16,7 +16,7 @@
     "require": {
         "php": "^8.2",
         "doctrine/coding-standard": "^12.0",
-        "slevomat/coding-standard": "^8.14",
+        "slevomat/coding-standard": "^8.15",
         "squizlabs/php_codesniffer": "^3.9"
     },
     "require-dev": {