Edit image docs to align with style guide

[nickmcintyre]

Increasing Access

Writing with plain, consistent language increases cognitive accessibility. It's also more welcoming to younger members of the community.

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 enhancement details

I'll edit the inline documentation and code samples for each function in the image group.