WASM support

[4t145]

Is your feature request related to a problem? Please describe.
Crate mcp-server use feature tokio/full which will cause compile error when target is wasm32.

Describe the solution you'd like
We should use features = ["io-util"]

Describe alternatives you've considered

Additional context
I made a PR to show how it works #15.

Being able to compile into wasi would be helpful, which makes us can download and run a same wasi file in every platform, instead of using python or npx.