Make Table of Contents Scroll Along contents of Guide and other Documentation

[wldcordeiro]

This would be a great feature on the site. Being able to jump to other parts from anywhere in the document without having to scroll back to the top again. Here, here, and, here in particular. Though adding scrollability to the left sidebar on the API Page would also be great.

[arslan]

I can try to work on this. Sounds like a good idea.

[edunham]

@rcx Did you have time to make this happen? Just checking in case there's un-PR'd code sitting around somewhere that would resolve the issue :)