optimize the docs site heading and add language switcher

[HelloRWA]

Hey, I'd like to optimize the heading of the docs site.

After we click on the Docs page, it shows a long list of menu and page links on the left.

I can optimize it to be the same style as the Vitepress official site.

I have read through the whole docs site, and I think I understand the whole docs now, and the new menu structure will be like this:

The screenshot is my Nuxt3 version of it, I understand that I need to build the structure in the Vitepress.

If permitted, I will start to work on this and make a PR for this including multiple language switchers with part of Chinese translation(We are working on progressing the whole docs into Chinese, about 50% for now).

AO from Stark@HelloRWA!

[HelloRWA]

@twilson63