Display chords of current progression, and which chord is active

[mickmister]

Definitely have some notes on this somewhere

I think I landed on the goal of making it so the user doesn't need to move their eyes or scan the page very much. They can look at one place and it will show them what's happening now and "next up"

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Original comment:

          TODO: this should pull from websockets instead of being hardcoded here

Originally posted by @mickmister in https://github.com/jamtools/jamtools/pull/29#discussion_r1380839026