BitBucket support

[vajnorcan]

Please add the support for BitBucket repositories. It uses the Git version control as well, so most of the implementation would be the same except probably the github releases. In a summary what it would do

• automatically number the version based on the conventional commits (basically a Standard-version plugin)
• update the change log
• create the release branch in the repo (gitflow) and finalise it

Support for Travis would be optional but that is already in place.

Thanks!

[dominique-mueller]

The way I see it, the only difference between BitBucket and GitHub that's interesting in this context is that BitBucket doesn't seem to have the concept of "Releases" / "Release-Pages". Thus:

• this "create release" task can be skipped completely
• collecting / requiring the GitHub API token wouldn't be necessary

Now the question is: How does one differentiate between GitHub and BitBucket? We could use the repository field in the package.json, it's actually being used today as well. This wouldn't then work for self-hosted BitBucket instances, though ... perhaps there's a way to find it out via the project's Git configuration?

All in all it seem do-able, I'll try to tackle this in the near future.