docs: add use-case for group API (#110)

* docs: add use-case for group API

Author: timonback

docs/configuration/configuration.mdx

@@ -88,7 +88,7 @@ Every custom extension field must begin with `x-`, for example `x-internal-id` (
 
 The standard AsyncAPI document contains all information, including channels, messages, schemas, etc.
 
-A group is a filtered view onto specific parts of the AsyncAPI document.
+A group is a filtered view onto specific parts of the AsyncAPI document, for example only the *public* or *consumed* interfaces.
 
 The group configuration must have a name (`group`). The `info` object can be adjusted and *at most* one matcher can be used: