Created by: piotr-cz
Replaced favicon with new one with sizes 48x48, 32x32 and 16x16, which are recommended by MSDN (more info in this SO answer)
File size is bigger (15.086KB vs 3.860KB), as previous favicon has used a PNG format, current uses Windows BMP. Gzipped files have comparable size.
As input I've used this file: https://github.com/facebook/react-devtools/blob/master/shells/webextension/icons/production.svg, but changed color from #59c9f1 to #61dafb as it's used in logo.svg and on https://reactjs.org/ site.
Followup of #3374