Add deno example with wasm-gc

[mizchi]

tl;dr

Add examples/deno. It works with --target wasm-gc without browser.

Why

wasm-gc was a helpful sample, but the browser setup was somewhat cumbersome.

The addition of WebAssembly for browser-compatible deno is an example of how moonbit can be used.

[peter-jerry-ye]

I would argue that we can just extract the js part from index.html to a main.mjs and achieve the same effect with the wasm-gc example.

Also I think we would need to determine the license of the project before accepting such a PR @bobzhang

[mizchi]

In fact, yes. However, many people are unaware of it without samples, so just having it on the examples list as a use case makes sense.
(I can't deny that I am a fan of deno myself.)

[peter-jerry-ye]

I adjusted the example in #186 for deno and node. What do you think?