Steam background preview per Ratot

Adds an input box to the top bar of the steam page to change the background of your profile easier and quicker. This box takes the link to a background that you can find on the steam market page (view full size) or other sites. Then when you are on a steam profile (your own or someone else's), you can preview how the background would look.

I made this because I found it annoying to inspect element everytime :)

Supports png/jpg/jpeg/mp4/webm.