PieSlice keyboard at Feature parity with circular keyboard

[x] Highlight keys
[x] Polygon viz-n (SVG)
[x] Arrow viz-n (SVG)
[x] Unify color scheme (no hardcoded colors, just variables)
[ ] Optional: Reuse color scheme at the CSS level (linear and PieSlice colors for black / white / selected should be inheriting from something common?)
[x] Make it test friendly (when i press F on the linear keyboard, the PieSlice key for F is also "selected").

alekslovestech / chromatic-circle