Add cross-reference from local_scheme config to implementations

Author: maresb

docs/config.md

@@ -17,6 +17,7 @@ Callables or other Python objects have to be passed in `setup.py` (via the `use_
 `local_scheme : str | Callable[[ScmVersion], str]`
 : Configures how the local component of the version (the optional part after the `+`) is constructed;
   either an entrypoint name or a callable.
+  See [Version number construction](extending.md#setuptools_scmlocal_scheme) for predefined implementations.
 
 
 `version_file: Path | PathLike[str] | None = None`