Fix for Steam's Library to hide the annoying "What's New" and/or "Shelf" section(s).
What started as a simple enough script on PasteBin — now with over 1.5K views (https://pastebin.com/WXbp8X46) — has now been modifed to have a nice little GUI.
Since I went that far, I decided to add auto-detection of the Steam directory, and some nice GUI elements to tell you the status of the offending CSS file, along with which of the two fixes have already been sorted.
I've added the original script purely for posterity reasons.