Alt to title per Marc Brillault

Copies images alt attributes to their title, so everyone can see the alt text while hovering the image
Alt attributes are meant to convey information about graphical elements (images, videos etc) so the visually impaired can still navigate your page without losing any context.

These attributes are not meant to be seen by a regular browser. But one can want to easily see which image has a correct alt attribute, for testing or debugging purposes, or just to see how thses alt attributes are used by others (And also _if_ they are used by others).

When installed, the extension will look for the page's source code, and duplicate the alt attribute into the element's title attribute, thus allowing to see the content by hovering the cursor on said element.

Changelog:

V1. Initial upload, works only with images (img tags). The script also looks for DOM changes, so if new images are loaded, their alt attributes are managed as well.