Integrate with rust-embed

[ogarcia]

I think it would be a very interesting idea for rocket to integrate with rust-embed so that it can directly consume the asset for static files.

Something like:

#[macro_use] extern crate rocket;
use rust_embed::RustEmbed;

#[derive(RustEmbed)]
#[folder = "css/"]
struct Asset;

#[get("/")]
fn index() -> &'static str {
    "Hello, world!"
}

#[launch]
fn rocket() -> _ {
    rocket::build().mount("/", routes![index]).mount("/css", embed(Asset))
}

Even going a step further, it can also be used when registering an endpoint (this is a not very good example, but just to make it clear).

#[derive(RustEmbed)]
#[folder = "css/"]
struct Asset;

#[get("/css/<path..>")]
pub async fn second(file_path: &str) -> Option<rust_embed::EmbeddedFile> {
    Asset::get(file_path)
}

This could also be used for templates, obviously losing the possibility to modify them on the fly.

What do you think?