Make docs fragment navigation update the navigation bar URL

[alilleybrinker]

Right now, when you click on an in-page fragment-identifier based link (the right hand navigation on the documentation pages of the site), it scrolls you to that location, but it doesn't update the URL in the navigation bar. This breaks workflows where someone wants to copy a link to a specific part of a page out of their navigation bar. The solution here would be to update the JS that handles scroll to update the nav bar specifically to reflect the navigated-to fragment identifier.