Add p5play

[mvicky2592]

Please confirm this pull request meets the following requirements:

• I followed the contributing guidelines: https://github.com/github/explore/blob/main/CONTRIBUTING.md.
• I am not the sole author or employee of a company who created either the topic I am modifying/adding or the collection entry I am modifying/adding.

Which change are you proposing?

• Suggesting edits to an existing topic or collection
• Curating a new topic or collection
• Something that does not neatly fit into the binary options above

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Editing an existing topic or collection

I'm suggesting these edits to an existing topic or collection:

• Image (and my file is *.png, square, dimensions 288x288, size <= 75 kB)
• Content (and my changes are in index.md)

Please replace this line with an explanation of why you think these changes should be made.

Curating a new topic or collection

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Something that does not neatly fit into the binary options above

• My suggested edits are not about an existing topic or collection, or at least not a single one
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• My suggested edits conform to the Style Guide and API docs: https://github.com/github/explore/tree/main/docs

p5play is a JavaScript game engine with +50,000 monthly users. https://p5play.org

Notably it's been used at Girls Who Code summer camps and CodeHS courses. v1 is also used by Code.org.

[ahpook]

New entry needs to be at the bottom of the list

[ahpook]

Thanks!