Added custom formatter to uploads limit

refs https://linear.app/tryghost/issue/CORE-121/create-a-video-storage-adapter

 - Provides readable bytes -> megabytes conversion for filesize limit

ghost/limit-service/lib/config.js

@@ -50,6 +50,9 @@ module.exports = {
         // NOTE: this function should not ever be used as for uploads we compare the size
         //       of the uploaded file with the configured limit. Noop is here to keep the
         //       MaxLimit constructor happy
-        currentCountQuery: () => {}
+        currentCountQuery: () => {},
+        // NOTE: the uploads limit is based on file sizes provided in Bytes
+        //       a custom formatter is here for more user-friendly formatting when forming an error
+        formatter: count => `${count / 1000000}MB`
     }
 };