KBFinder for firefox per rquinzio

Finds KB identifier for you on Microsoft support pages with just the click of a button.
Do whatever you want with the code, feel free to improve it since i'm no dev and my dev skills level is 0.
Hope it helps you.
Huge thanks to pkjain (https://github.com/pkjain). Most of the code is from one of his tutorials : https://infoheap.com/chrome-extension-tutorial-access-dom/