Does gem rdoc have a way to include additional html files in the output?

I would like to include custom html in along with the generated html from my
source code.

Is there an easy way to do this so that when the gem rdoc command is run
that it copies this additional html to the gem rdoc path so that it can be
linked to?

I want to end up with a mix of rdoc and hand crafted html that one can jump
back and forth to using when browsing the documentation using gem_server.

Thanks in advance,

Jeff