Curate: playdate topics

[boozook]

Please confirm this pull request meets the following requirements:

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• 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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Curating a new topic or collection

• I've formatted my changes as a new folder directory, named for the topic or collection as it appears in the URL on GitHub (e.g. https://github.com/topics/[NAME] or https://github.com/collections/[NAME])
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I'm adding two new dependent topics:

• playdate (device, generic topic)
• playdate-sdk (SDK-related things, development)

First one playdate is more generic and I have seen many repositories with libs, frameworks, engines and games made for playdate, marked with this topic. Also projects like https://github.com/cranksters/playdate-reverse-engineering .

The second is playdate-sdk that concrete about the SDK, bindings/externs and development for platform in general.
There are many projects with bindings for various languages such as swift, rust, nim, that marked with playdate-sdk topic. Also there are could be tools such as docs/code-generators and other tooling that uses SDK.

❗️ I'm adding two new topics because one depends on the other and they are both integral and necessary to each other.

[ahpook]

Nice, LGTM! 🤖 🕹️