Catch PopState Event (goback) and Redirect to popNavStack

[mreyesh]

Minor UX enhancement:

Catch PopState Event (goback) and Redirect to popNavStack so that if you are exploring in the explorer and traverse a path of links, you can go back by using the go back browser button or any shortcuts from the keyboard or trackpad/mouse.

[nezaj]

Thanks for the PR @mreyesh !

I noticed there's a slight bug with this. I can make things work like so:

• Start at home-page, click dashboard, go to explorer, find a namespace with a link, traverse the link
• Going backwards and forwards should work!

However navigation will break like so:

• After traversing a link go backwards enough to end up on the home page
• Now click forward button, you'll be back in explorer, and if you traverse a link, hitting the back button takes you to the home page

I think the problem lies with how we use router.replace -- I think we may want to switch to just using push throughout instead.