Allow Rust workers to return an array of bytes instead of a String. Note that wws serializes the worker output as an UTF-8 JSON, so an arbitrary array of bytes may not be serializable. For this reason, we implemented this feature using base64 to encode the output when the worker exports an array of bytes.

Then, wws will look for the base64 flag in the serialized JSON. If it's true, it will perform the decoding process before sending the result back.

The feature introduces a breaking change as we cannot now set the response body type as String. I created a new Content enum that can represents both text and base64 responses.

The change is pretty trivial:

# Before
fn handler(_req: Request<String>, cache: &mut Cache) -> Result<Response<String>>;

# After
fn handler(_req: Request<String>, cache: &mut Cache) -> Result<Response<Content>>;

Thanks to the implementation of the From trait, the way you pass the body to the response will continue as it's now:

Ok(http::Response::builder()
    .status(200)
    .header("x-generated-by", "wasm-workers-server")
    .body(response.into())?)

The statement response.into() will initialize the right Content enum type.

The PR also updates the documentation and adds a new fun example called pdf-create.

It closes #44