curate: AsyncAPI specification

[Pakisan]

Please confirm this pull request meets the following requirements:

• [x] I followed the contributing guidelines: https://github.com/github/explore/blob/main/CONTRIBUTING.md.
• [x] 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
• [x] 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

• [x] 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])
• [x] My folder contains a *.png image (if applicable) and index.md
• [x] All required fields in my index.md conform to the Style Guide and API docs: https://github.com/github/explore/tree/main/docs

Here is already bunch of tools who are working with our specification. It's time to format properly our topic and provide needed information for further discovering of our specification, when users are looking trough our topic

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