Given that we now have a clear separation between UI widgets (ones used at the Mozilla level of products) versus Domain-specific UI widgets (ones used in a specific domain or location in Firefox), we should modify the existing ./mach addwidget command to handle this new case.

Since domain-specific UI widgets will not live in toolkit/content/widgets, the command will need to be modified to take in a file path so that:

• the generated files are put in the proper location
  • This includes adding the [xyz].stories.md file to browser/components/storybook/stories!
• the correct jar.mn file is modified
• If a chrome.ini file lives somewhere near the passed in file path, then add an entry for the newly generated file.
• If there are no chrome tests near the passed in path, then:
  • Create a chrome.ini file in the appropriate location
  • Modify the relevant moz.build by adding MOCHITEST_CHROME_MANIFESTS += ["[xyz]/chrome.ini"].
    • Some directories use test/chrome, others use tests/chrome and some just use test/

I think we can keep the existing behavior as-is: if no file path is given, then the generated widget must be a "UI widget" and not a "domain-specific widget".