It seems your add-on/the whole thing has been included in Firefox 71?
https://www.ghacks.net/2019/08/27/firefox-71-has-a-new-certificates-viewer/
So is this still useful/is there any advantage?
If yes: Could you please describe what? Maybe best also state/adjust that in the Readme, AMO description etc.
If not: Could you somehow deprecate this add-on? AMO description & Readme again. Possibly another update that just tells users where that new functionality is?
Possibly even archive this repository, to mark it as unmaintained.