Bundle our licenses correctly in our npm packages

[nolanlawson]

There are two issues right now with our licenses:

1. We don't actually ship a LICENSE file in each of our monorepo sub-packages – we just put "license": "MIT" in the package.json.
2. In some cases we pre-bundle our own dependencies to avoid CJS/ESM compat issues. We should redistribute the correct license as necessary.

I did a check of all these bundled dependencies:

• estree-walker (MIT)
• parse5 (MIT)
• @parse5/tools (MIT – missing an actual LICENSE file though)
• entities (BSD)

This also needs to be done carefully since some tools like https://socket.dev actually warn when a package contains multiple LICENSE files.