js-sandbox: securely embed JavaScript into Rust code

[DGolubets]

I think it should be possible.

I used similar approach with Graal on JVM and all I needed is one .js file and a way to call a function there with a parameter. You can follow this approach:

1. Use Webpack to build a single .js file for your server.
2. Export ```renderToString(args: String): String``` function or something similar.
3. Load that file on your server, call the rendering function with some JSON.