Show Anchors 2 compatible with recent versions of Firefox Puntuado con 3 de 5 estrellas

I have taken over the Add-on and maintain a version that is compatible with the most recent version of Firefox: https://addons.mozilla.org/en-US/firefox/addon/show-anchors-2/

The code is based on Show Anchors, many thanks to its original author, and on changes made by Peter.