Per that page, it should be sufficient to "just" publish this extension on addons.mozilla.org ("just" being in scare quotes due to my unfamiliarity with how stringent Mozilla's policies might be in terms of what's signable). Alternately, there's a signing API that can be used.
I'd try my hand at it myself, but I don't want to step on your toes unless I have explicit authorization to do so.
Relevant information from Mozilla: https://wiki.mozilla.org/Addons/Extension_Signing
Per that page, it should be sufficient to "just" publish this extension on addons.mozilla.org ("just" being in scare quotes due to my unfamiliarity with how stringent Mozilla's policies might be in terms of what's signable). Alternately, there's a signing API that can be used.
I'd try my hand at it myself, but I don't want to step on your toes unless I have explicit authorization to do so.