Multi-track support

[grahammccarthy]

Multi track support.
Defraz made it work! 🙏

[grahammccarthy]

Defraz's is better.

[grahammccarthy]

@defraz the only issue with this code is that you can't link directly to a growth assessment like the previous version. I can't seem to figure out where / how the route logic works.

But if you were to go to: http://localhost:3000/engineering#3,2,2,1,2,3,3,0,1,1,1,0,2,3,3,2,Soapbox%20Simon,Senior%20Engineer

Directly, it loads up the empty state.

Once that is fix, this can be merged in, and all the links people have done to the growth assessment will need to be updated.