add keyboard shortcuts to open and download image files quicker
Adds custom keyboard shortcuts to :
open the image under cursor in tab: ALT key.
download image under cursor: SHIFT + w (or z depending on layout)
This is mainly intended for Tumblr image posts.
If you feel that you can improve the script, feel free to do so.
The code is awful right now, until I learn more about javascript and clean it up.
But at least it's functional most of the time, unless some weird iframe structure comes into play, need to fix that.
Credits to Dimethyl's https://greasyfork.org/scripts/9014-tumblr-image-size for the tumblr image size trick.
I hope he updates it to the actual best quality version as discussed.
