Curate the dsh-plugin topic

[zevorn]

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

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.
• My folder contains a *.png image and index.md.
• All required fields in my index.md conform to the Style Guide and API docs.

dsh-plugin is already used by more than 2,000 public repositories and by
the official DeepSeek Harness repository. It identifies a broad ecosystem of
reusable tools, interfaces, integrations, and local capabilities. Curating the
topic gives developers a stable description and links to its official project.

The submitted PNG is derived from the official DeepSeek Harness favicon:
https://github.com/deepseek-ai/deepseek-harness/blob/master/apps/web/public/favicon.svg.

[zevorn]

Closing as a duplicate of #5347. The curated dsh topic already declares dsh-plugin as an alias and includes the official 288x288 logo. The public Topics page is waiting for GitHub's periodic Explore sync.