Firefox is deprecating it's old extensions, and is moving to WebExtension.
To use WebExtension, use the Native Messaging API and a client-side external program.
https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Native_messaging
The external program will need to be OS-specific, so it may be beneficial to use something like Python that works in Linux, Windows, MacOS.
Firefox is deprecating it's old extensions, and is moving to WebExtension.
To use WebExtension, use the Native Messaging API and a client-side external program.
https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Native_messaging
The external program will need to be OS-specific, so it may be beneficial to use something like Python that works in Linux, Windows, MacOS.