Add selfhosted wakatime integration (wakapi)

[MeerBiene]

This PR adds the option to use a selfhosted wakatime instance for the wakatime plugin.

I tested it against this project called Wakapi which mimics the same endpoints as wakatime does, so its just a matter of using a different api url

[lowlighter]

Thanks a lot for your contribution 👍 !
I requested some changes but nothing major 🙂

[MeerBiene]

I think I got everything resolved, let me know if otherwise :)

[lowlighter]

Almost!
Since plugin_wakatime_apiurl has been renamed to plugin_wakatime_url the inputs parser will send back url instead of apiurl 🙂

After this it should be ok 👍
(builds are currently broke because I'm experimenting stuff with vercel so it's ok)

[lowlighter]

Thanks!