`wasm` / workers target for `dx bundle --platform web --fullstack`

## Feature Request

To support targets like Cloudflare workers for `dx bundle`, we should allow some sort of configuration for bundle that builds your server as a `.wasm` module. Ideally the output `dx bundle` format matches the cloudflare workers format so we could eventually support `dx deploy --hosting cloudflare-worker`.

This is generally not that hard and would very useful! The main challenge here is simply designing the configuration frontend since the CLI already accepts different targets for the server.