Add support for yarn

[BuonOmo]

I came back over an old fork I've made that supported yarn completion. And I went through my mind that it could fit together in the same app. If you're in, just tell me :)

[aquadesk]

Please tell him!

[BuonOmo]

@aquadesk I think this is unmaintained unfortunately, feel free to use both my fork and this project :)