adds github links and adjusts a:hover color

[stebogit]

I always look for these!

Link to Turf library:

Link to package:

[stebogit]

ping @rowanwins 👋🏻

[rowanwins]

Finally finally looking at updating the docs @stebogit

I just wanted to double check on the npm link if it should link to npm or the github package - it seems to me that linking to the github package might be a little misleading when the text says npm... any thoughts?