Add an option to prevent quick unbookmarking

[teddy-gustiaux]

The idea is to still be able to quick bookmark via the dedicated star icon, but to prevent accidental deletion by clicking on the icon by mistake again or at a latter time.

A simple on/off option in the add-on settings would do the job. The setting should be off by default (i.e. preventing quick unbookmarking should be a mindful choice by the user).