Update project docs and branding

[Evenss]

Summary

• Reframe the project as a metro typing game that can support multiple cities
• Document supported cities, online play, game modes, local startup, and inspiration
• Add an English README with language links between both versions
• Add the selected branded favicon and retain the favicon design exploration assets

Why

Make the project purpose and ways to play immediately clear in both Chinese and English, transparently acknowledge the original inspiration, and give the site a recognizable browser icon.

Impact

Visitors get clearer project documentation, an English version, and updated browser branding. Application gameplay is unchanged.

Checks

• git diff --check main...HEAD
• npm test — build succeeded and 3 tests passed