Add support for automatically generating the return type in wasm_export macro

[findolor]

Currently we are using "unchecked_return_type" directly on the function to specify the return type on typescript. This can be generated from functions return type and applied automatically inside the macro.

[rouzwelt]

I have made this PR in wasm_bindgen upstream repo about 2 month ago that add this feature natively to wasm_bindgen, but looks like the repo has been quiet for past month after our last PR, there has been no new merge to main.
Let's keep an eye on this and once merged we should have that fixed natively.

wasm-bindgen/wasm-bindgen#4455