[Web Extension] Add content script world property to manifest schema validation

[carterworks]

↪️ Pull Request

Resolves #9482.

Adds the isolation context property world to the @parcel/transformer-webextension schema validation code.

It's Chrome-only currently, but I think that Firefox support is currently on the way.

💻 Examples

This following manifest.json would throw an error while validating the schema because of content_scripts[0].world

{
  "name": "MV3 Migration - content script example",
  "description": "Source: https://github.com/GoogleChrome/chrome-extensions-samples",
  "version": "0.1",
  "manifest_version": 3,
  "background": {
    "service_worker": "background.js"
  },
  "permissions": [
    "scripting",
    "activeTab"
  ],
  "content_scripts": [{
    "matches": ["https://*.google.com/*"],
    "js": ["other-content-script.js"],
    "world": "ISOLATED"
  }],
  "action": {
    "default_popup": "popup.html"
  },
  "side_panel": {
    "default_path": "side-panel.html"
  }
}

🚨 Test instructions

cd packages/core/integration-tests && yarn test test/webextension.js

✔️ PR Todo

• Added/updated unit tests for this change
• Filled out test instructions (In case there aren't any unit tests)
• Included links to related issues/PRs

[carterworks]

@101arrowz or @mischnic Please review this.
This does block me on a work project, but I'll patch it locally until this PR is merged and released.