Feat/web 943 playspeed design

[1t1e1]

I didn't complete #943, so I think it would be beneficial to make my progress, notes, etc. public here.

[1t1e1]

Remain Todos for window.prompt version

• style fixes
• validation for input from window.prompt, check error message.
• check all TODO:SS before merge

Todos for Slider component with modal

• Design Slider Component
• Look at how Login modal works
• etc.

[mitchdowney]

@1t1e1 awesome, thanks for sharing your progress!

I will be mostly away from a computer this week, so I apologize in advance if I don't get to this as soon as I'd like. It might not be until next week when I could review and merge (or finish it and merge).