docs: improve godoc for trees and lists

[bashbunni]

WIP: improving godoc given my experience checkin' out the API

• [x] provide basic usage examples in godoc
• [x] explain parameters if less obvious (StyleFunc)

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Viewing changes: godoc -http=localhost:6060 then connect to localhost:6060 in browser. From there, look at the list and tree godoc

[bashbunni]

I think the StyleFunc examples explain the parameters well enough... If it's unclear going forward, then can always add to the docs later