docs: add English README

[webbrain-one]

Adds README.en-US.md alongside the original documentation.

Generated by qwen3.6-35b-a3b via local API.

[Zhao73]

Thanks for the contribution. A change is needed before this can be merged:

The repository already has an English README at README.en.md, and the language badges in both the Chinese README and this new file point to README.en.md. Adding README.en-US.md therefore creates a second, orphaned English README and two copies that can drift independently.

Please update the existing README.en.md with the fuller translation instead. If the intent is to rename it to README.en-US.md, please remove/replace README.en.md and update the English badge links in both README files in the same change. Also remove the two leading blank lines from the new document.

I verified the other relative documentation/image links and the advertised repository files; those paths currently exist. No GitHub checks have run for this PR yet.