docs: add dsh-market friendship link

[wisdomqin]

What changed

• replace the outdated model-provider section in both READMEs with a Friends/友情链接 entry for dsh-market
• place the friendship entry immediately before Quick start/快速开始
• keep the English and Chinese documentation aligned
• align the release-contract test with the generic update source already configured on main

Why

dsh-market lists DSH Desktop in its Friends section, and DSH Desktop now reciprocates with a concise description of the community plugin market.

The release test still expected the previous GitHub updater provider after main switched to the official generic update endpoint, which made every new PR fail independently of its diff.

Validation

• git diff --check
• verified heading order in both README files
• verified the live registry currently contains more than 900 plugins
• npm test (59 passed)
• npm run typecheck
• npm run build