Launch web worker

Highly WIP. Current usage:

```rust fn startup() { let worker = workerfromrunner("MyRunner", "mypkgname").unwrap(); }

[wasm_bindgen]

pub struct MyRunner;

[wasm_bindgen]

impl MyRunner { pub fn new() -> Self { Self }

pub fn init(&self) {
    console::log_1(&JsValue::from_str("MyRunner initialized"));
}

pub fn onmessage(&mut self, msg: MessageEvent) {
    console::log_1(&format!("MyRunner received: {msg:?}").into());
}

} ```