build: configure webpack to handle UMD emits

[justinmk3]

The vscode-json-languageservice module includes ESM and UMD emits, but sets the UMD output as the main one. Our webpack config needs extra configuration to ignore UMD distributions to avoid issues like this

• reference:
  • https://dev.to/iggredible/what-the-heck-are-cjs-amd-umd-and-esm-ikm
  • https://weblogs.asp.net/dixin/understanding-all-javascript-module-formats-and-tools
  • build(deps): unwrap UMD imports for JSON language service #2141