Add public on some visualizations views

[ipodishima]

Motivation:

I'm working on some recording visualizations and discovered:

• SpectrogramView initializer was not public
• NodeRollingView could benefit from more control on configuration for reuse.
• Opened FloatPlot and FragmentBuilder so that people could their own components based on those two

[aure]

Thanks!

[Matt54]

@ipodishima - do those colors in the SpectrogramView need to be Bindings? My guess is that they can just be variables (not State or Binding)

[Matt54]

Let me know if I'm off on this: https://github.com/AudioKit/AudioKitUI/pull/63

[ipodishima]

Those were states before, this is why I kept bindings. But I'm not sure this is useful even though it's not lost to have bindings @Matt54

[Matt54]

@ipodishima I'm pretty sure I made them state when I had a "less than ideal" understanding of SwiftUI state management 😅 - I should probably do a full sweep through AudioKitUI and clean up my mess

[ipodishima]

Ahahaha no worries. I'm still trying to figure out the best practices for SwiftUI without being redundant, creating bugs, or having performance issues 🤣