Automatically reveal hidden HTML elements από NateN1222

**Version 1.8**
Made the CSS unhiding more effective and the prompt to unhide HTML a lot less annoying.
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An add-on that is meant to fix CSS related bugs on browsers that don't run non-free Javascript.

Often times proprietary scripts that handle frame killers (https://en.wikipedia.org/wiki/Framekiller) get blocked and this causes pages not to be hidden.

It has been found to work for websites such as medicare.gov and dmca.copyright.gov.

This add-on assumes that you are running LibreJS and was tested on the latest version of GNU IceCat, a version of Firefox.

For more info about non-free Javascript and why it should be avoided:

https://www.gnu.org/philosophy/javascript-trap.en.html