Add logo and favicon

[defect]

This adds the logo @michaeljs1990 kindly gave collins in #542. Thank you! The favicon file contains 16x16, 32x32 and 64x64 sizes. I wasn't really sure where to put the original image so i just added it next to the favicon.

I had to add a little bit of horizontal space for the image to be square. Here's the full process i used in case anyone wants to tweak the paramaters:

convert logo.png -gravity East -background transparent -splice 175x0 step1.png
convert step1.png -gravity West -background transparent -splice 72x0 step2.png

for geom in "16x16" "32x32" "64x64"; do
    convert step2.png -thumbnail "$geom" "$geom.png"
    optipng "$geom.png"
done

convert 16x16.png 32x32.png 64x64.png favicon.ico
rm 16x16.png 32x32.png 64x64.png step1.png step2.png

In the end, it looks like this in chrome:

@michaeljs1990 @byxorna @roymarantz

[michaeljs1990]

niceeee, thanks for putting up the PR!

[michaeljs1990]

Fun fact, the logo cost me 0.5 Bitcoin but at the time of purchase that was only ~100$.