Add p5.strands examples on regular p5 functions that can be used in a strands context

Increasing access

This supports the effort of making strands more visible in the reference, and also makes it clearer what can and can't be used within p5.strands. For example, while we now support random(), it may not be clear from the random() reference page that it can be used in a shader. Having maybe one strands example for each of these would be helpful.

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
• Internationalization
• Friendly errors
• Other (specify if possible)

Feature enhancement details

We maybe want to put strands examples last, and have a bit of explanation above them saying that they can also be used in shaders. To interleave examples with explanation, examples must be written as inline example blocks: https://github.com/processing/p5.js/blob/dev-2.0/contributor_docs/contributing_to_the_p5js_reference.md#inserting-examples-within-the-description