Override default search engine setting

Hi

I am new to FF extension and I will be making my first extension for same.
I have made few extension for chrome and safari.

My main work of this extension is overriding default search engine as we do using “chrome_settings_overrides” for chrome but as this question I can see that mozilla do not support override settings at the moment.
Can you please share when you will add this feature?

It looks like its in the works - https://bugzilla.mozilla.org/show_bug.cgi?id=1301315