config: add alias from `hg help rhg` to `hg help rust`
This will make using `rhg` more user-friendly and features more
discoverable.
= Mercurial XXX =
== New Features ==
== Default Format Change ==
These changes affect newly created repositories (or new clones) done with
Mercurial XXX.
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
== Internal API Changes ==
== Miscellaneous ==