Add the support of fs and env

[DarumaDocker]

https://github.com/second-state/wasmedge-quickjs/blob/main/example_js/react18_ssr/main.mjs#L8
Currently, the CSS can only be imported as a module in the example.

But in reality, the assets will be built with some random file names, something like main.073c9b0a.css.
This requires the server can read the content from the file system.

As Wasi has supplied the files and env API, it would be great to add modules like 'wasi_fs' and 'wasi_env`.

[L-jasmine]

About fs. In quickjs 'std' module has some function.
If you need other fs function, please tell me more.

About env. I don't know what function is needed. Can you show me how you want to use it?

[DarumaDocker]

In Nodejs, I can get environment variables via process.env. The typical scenario is to set its port when the server starts.

[L-jasmine]

#44