Add a way to read back pixels from p5.Framebuffer

[davepagurek]

Increasing Access

Once initial framebuffer support is merged #6072, ideally, we will make framebuffers work as similarly as possible to p5.Graphics so that they do not have a steep learning curve for existing p5 users. This includes letting users read pixels the way they might in a p5.Graphics.

Most appropriate sub-area of p5.js?

• Accessibility
• Color
• Core/Environment/Rendering
• Data
• DOM
• Events
• Image
• IO
• Math
• Typography
• Utilities
• WebGL
• Build Process
• Unit Testing
• Internalization
• Friendly Errors
• Other (specify if possible)

Feature request details

This would likely include:

• loadPixels() and pixels support
• get(x,y) support and get() support
  • I was sent this code snippet earlier for turning a framebuffer into a p5.Image (similar to get()), which I put into an issue in another repo for reference: Support .save() for framebuffers davepagurek/p5.Framebuffer#23
• Possibly updatePixels (but this can maybe be separate and be done along with updatePixels() can't be called in WEBGL Mode #5155)