Support autobazel with `repository_rule`s

[adamtheturtle]

I have a repository_rule as per https://docs.bazel.build/versions/master/skylark/repository_rules.html.

It seems impossible to use autobazel to document this.

[danwos]

Thanks for the issue.
To be honest I have absolutely no idea when I find some time to fix this or enhance the lib, as I have currently no project which is using Bazel.

So if you like to support here, you are strongly welcome.

[adamtheturtle]

Thanks - no promises just yet - for now just issues and maybe minor patches but if possible I'll try to contribute properly!