Merge pull request #18 from sourceboat/dependabot/composer/slevomat/coding-standard-6.4.0

Update slevomat/coding-standard requirement from 6.0.8 to 6.4.0

Author: Kevin Buchholz

composer.json

@@ -37,7 +37,7 @@
         "orchestra/testbench": "^5.0 || ^6.0",
         "phpmd/phpmd": "^2.6",
         "phpunit/phpunit": "9.*",
-        "slevomat/coding-standard": "6.0.8",
+        "slevomat/coding-standard": "6.4.0",
         "squizlabs/php_codesniffer": "^3.5"
     },
     "autoload": {