Add Hangzhou Dianzi University (HDU)

[CSharperMantle]

Please confirm this pull request meets the following requirements:

• I followed the contributing guidelines: https://github.com/github/explore/blob/main/CONTRIBUTING.md.
• This change is not self-promotion.

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

The topics hdu and hangzhou-dianzi-university contain quite a few hot repos, all related to school life, projects, and works at Hangzhou Dianzi University. It would be better to consolidate these topics and create a unified topic for HDU.

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Please note: we will close your PR without comment if you do not check the boxes above and provide ALL requested information.

[Copilot]

Pull request overview

This PR adds a curated topic entry for Hangzhou Dianzi University (HDU), consolidating existing community usage of the hdu and hangzhou-dianzi-university tags into a single, well-defined topic in github/explore.

Changes:

• Add topics/hdu/index.md with front matter (topic slug, display name, alias, logo, URLs, and short description) and a one-paragraph long description of HDU.
• Add topics/hdu/hdu.png as the logo referenced by the new topic metadata.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated no comments.

File	Description
topics/hdu/index.md	Defines the new hdu topic metadata, including alias to hangzhou-dianzi-university and basic university description.
topics/hdu/hdu.png	Provides the logo asset referenced by the new HDU topic.

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