[Javascript] Fix broken package entrypoints

[Codex-]

Currently as of 4.13.1 the entrypoint for browser is invalid, and main specifies the esm build instead of the commonjs one.

This results in commonjs based sources attempting to load esm syntax when addressing the sources using main.

The error in browser causes this error when attempting to bundle the sources:

[commonjs--resolver] Failed to resolve entry for package "antlr4". The package may have incorrect main/module/exports specified in its package.json.
error during build:
Error: Failed to resolve entry for package "antlr4". The package may have incorrect main/module/exports specified in its package.json.

Fixes

• browser field updated to fix the extension
  • "dist/antlr4.web.js" -> "dist/antlr4.web.mjs"
• main field updated to point to the commonjs bundle
  • "dist/antlr4.node.mjs"->"dist/antlr4.node.cjs"`

Added

• module field to point to the esm bundle
  • "module": "dist/antlr4.node.mjs"

More information on main vs module can be found here: https://nodejs.org/api/packages.html#dual-commonjses-module-packages

[ericvergnaud]

Thanks for this
@parrt blessed