feat: add support for extracting URLs from Firefox browsers

[BelKed]

[!IMPORTANT] Adds support for extracting URLs from Firefox browsers using AppleScript in the MainThing class.

• Behavior:
  • Adds support for extracting URLs from Firefox browsers using AppleScript in MainThing class.
  • Handles Firefox, Firefox Developer Edition, and Firefox Nightly.
  • Uses AppleScript to extract URL from Firefox's UI hierarchy.
• Code:
  • Adds FIREFOX_BROWSERS list in MainThing.
  • Implements getFirefoxURL() function in windowTitleChanged() to extract URL.
  • Updates pollActiveWindow() to detect Firefox browsers and extract URLs.

^{This description was created by for e1975ee948d23f8cc176b1bb45a0be74fcc719a0. It will automatically update as commits are pushed.}

[BelKed]

No, Firefox does not expose the same Apple Events APIs for accessing tab and window information like Chrome and Safari do on macOS. This is why we have to use AppleScript to interact with Firefox's UI elements through the Accessibility framework instead :)