i18n: update chinese

[deluxghost]

Good project! I haven't seen any other modern and active yt-dlp webui yet. Still needs format selection tho.

Suggestion:

1. use placeholder in strings like toastConnected:

toastConnected: 'Connected to %1'

and replace them with dynamic content at run time.

This makes translating process easier.

(The %1 above is just an example, I don't know how nodejs works)

2. add a field for language display name, instead use the map key directly?