There's not an extension but there is an app (available as apk or from F-Droid/Google Play). The app contains all your bookmarks and easily searchable, you click on the bookmark and it opens in whatever your default browser is, in my case it's Fennec. Not as easy as just typing in the search bar in the browser but it's a small cost for not having a Mozilla account (I've nothing against Mozilla but the fewer big organisations who have my data, the better).