add introductions of project architecture in docs

[LoTwT]

description

Introductions of project architecture in docs may help potential contributors get started and contribute more quickly and easily.

Also, I think the design of RPC communications and bridgeRpc is interesting. I think it's a good topic to share with others. 😊

expect

• dependencies graph of packages
• introductions of bridgeRpc
• RPC and vite contexts
• introductions of API references in different packages and runtimes
• ...

[webfansplz]

Of course, this is in our plan, and we will introduce them in the documentation (when they are more stable).