Add Github integration for all repositories

We need to enable all of the repositories for the issue linking and enable new repositories automatically.

Currently, within the GitHub integration page we need to provide the repository names explicitly. I am not sure if this is the target extension that we should use, but we would like to enable aha-GitHub integration for all current and future repositories without a need to provide their list within the extension page - this will simply not scale with number of repositories we have and changes we do for them.