Venu support?

[brownianmotion]

Thanks for making such a useful app, and making it open source.

I have a Venu, and was looking for an app like this. I noticed that it claims to not support Venu, so I'm seeing if I can add support for it.

This is my first foray into Garmin coding, so if you have a clue about any obvious things which would be needed for Venu support, please let me know. Otherwise hopefully I can figure it out and submit a pull request soon.