Create new page displaying witness schedule

I find it useful to have a new page, separate from witness and main pages, which renders the current schedule of witnesses producing blocks similar to how it is currently being rendered under https://hive.arcange.eu/schedule/

This shows who is currently producing blocks, top 20+1 witnesses, but also the pending schedule for upcoming block production.

This page can be linked in the menu next to the "Witnesses" link

Below is screenshot of referenced implementation