Update webpack plugin to support module workers

[RoccoC]

This is a proposed fix for #4741 .

This PR updates the monaco-editor-webpack-plugin's getWorkerUrl to add support for module workers. The function now checks if import.meta is defined, and if so, uses import to load the worker script. Otherwise, it falls back to using importScripts for classic workers.

[RoccoC]

@microsoft-github-policy-service agree

[ginna-baker]

Bump -- could really use this for my team