ReScript: camelCase to snake_case

1. First, create a branch on rescript-compiler folder

2. Install deps:

npm i

3. Run script

node main.js /path/to/rescript-compiler

4. Run dune build -w on rescript-compiler folder. Dune will report two erros on file jscomp/frontend/ppx_entry.ml

File "jscomp/frontend/ppx_entry.ml", line 34, characters 10-24:
34 |       let open Js_config in
               ^^^^^^^^^^^^^^
Warning 44 [open-shadow-identifier]: this open statement shadows the value identifier jsx_version (which is later used)
File "jscomp/frontend/ppx_entry.ml", line 35, characters 43-54:
35 |       let jsx_version = int_of_jsx_version jsx_version in
                                                ^^^^^^^^^^^
Error: This expression has type jsx_version option ref
       but an expression was expected of type jsx_version
Had 2 errors, waiting for filesystem changes...    

Rename jsx_version to jsx_version_

-   | Some jsx_version ->
+   | Some jsx_version_ ->
      let open Js_config in
-     let jsx_version = int_of_jsx_version jsx_version in
+     let jsx_version = int_of_jsx_version jsx_version_ in

5. Commit changes.

6. Run dune fmt dune build @fmt --auto-promote

7. Some renames were not good, they are few and can be done by the editor manually.