Add example for streaming a file in Rust

[radu-matei]

This commit adds a simple example showing file streaming in Rust.

[rylev]

Suggested change

	async fn handler(req: IncomingRequest, res: ResponseOutparam) {
	stream_file(req, res).await.unwrap();
	}
	async fn stream_file(_req: IncomingRequest, res: ResponseOutparam) -> Result<()> {
	async fn handler(req: IncomingRequest, res: ResponseOutparam) {
	if let Err(e) = stream_file(req, res).await {
	let response = e.into_response();
	// TODO: set response into out param
	}
	}
	async fn stream_file(_req: IncomingRequest, res: ResponseOutparam) -> Result<(), impl IntoResponse> {

We could do the above. We don't have a great way to take an http::Response<Vec<u8>> and set it in the ResponseOutparam but we can add that. I think that would make this much nicer.

[rylev]

Approved this but I do want us to come up with a better way to handle errors other than unwrapping.