fix: use empty polyfill if browser field is false

[markdalgleish]

Please describe the changes this PR makes and why it should be merged:

Fixes remix-run/remix#7095 (comment).

The change you made to made to the browser field PR is actually the way I originally wrote it too, but in my local testing it caused the issue raised in the comment above. Sorry for not calling this out in the original PR.

As noted in the comment, I prefer the way you wrote it, but since it's a breaking change for Remix v1 consumers, I'm hoping we can hold off on this until a major release.

Status and versioning classification:

• Code changes have been tested and working fine, or there are no code changes

[MichaelDeBoey]

Not sure if already handled, but since I was working on remix-run/web-std-io#43 (which added an exports.browser field) and came across this PR, I just wanted to let you know about the existence of the exports field (more info, see: https://nodejs.org/api/packages.html#exports).

If I'm correctly informed correctly (according to uuidjs/uuid#616 (comment)) the exports field is preferred over browser/main/module/types/...

[markdalgleish]

@MichaelDeBoey This is a different concept. This is about swapping out package internals rather than its public API. In this case we only care if they're swapping out Node builtins, e.g.

{
  "browser": {
    "crypto": false
  }
}

Or

{
  "browser": {
    "crypto": "./polyfills/crypto.js"
  }
}

[imranbarbhuiya]

Thanks, I'll release in a few hrs