Resolving Bugs and Expanding Documentation for WebGL in p5.js

My proposal is to resolve a number of outstanding bugs with WebGL functionality in p5.js, as well as expand on the documentation and tests for that functionality. While the WebGL components of p5.js are increasingly robust, there are a number of open issues that point towards some unexpected behavior and a lack of documentation around certain features. There is also the challenge of structuring the WebGL functions in a way that achieves parity with the p5.js approach to 2d rendering. There are a number of bugs that I would like to resolve, including #5455, #5631, and #5440. For documentation, it seems necessary to make certain additions to better orient developers who are new to 3D graphics and shaders, including graphics quirks that go beyond p5.js, such as the depth sorting challenges mentioned in issue #5420. I would also like to contribute documentation that helps users better understand the structure of WebGL in p5.js, information that is currently only available within the contributor documents. Additional examples would also be helpful for topics like setting up an effects chain or for achieving certain effects such as feedback.