target="_blank"-toggler von Augnustin

This extension was developed along this blog post:
https://augustin-riedinger.fr/en/resources/thoughts-on-target-blank
Go read it for full-context.

It does basically two things:
1. Changes the cursor to the logo when hovering a `target="_blank"` link
2. Toggles the `target="_blank"` attributes on links while pressing `Ctrl`/`Cmd` + `Shift`