add earlybird debugger support

[Mng12345]

Hi, i add earlybird debugger support in my fork of rescript-vscode. I think the visual debugger support can let more people easily to understand the OCaml analysis code logic and participate into our rescript-vscode development.
Here are the steps to initialize.

1. opam install earlybird
2. select OCaml earlybird(experimantal) item in RUN AND DEBUG in vscode.
3. add some breakpoints in the code, then everything is fine.
   The earlybird is much useful than i ever thought, currently some breakpoints may not be worked, may be some bugs exist in earlybird, just try again.
   

[fhammerschmidt]

@nojaf you mentioned somewhere you want a better debugging experience here, this might be helpful.

[nojaf]

I tried it, and I found it to be quite lackluster and limited.

[fhammerschmidt]

So can we close this then?

[nojaf]

We could maybe revisit this over at https://github.com/rescript-lang/rescript/, since we move the analysis code over there now.

@Mng12345 did this ever work well for you? I found that not all breakpoints were working for me.