add isoverse hexagon

[sebkopf]

[hexagontruth]

Two things:

1. Both the SVG and PNG have alpha transparency on the image itself, on the main gray background at least. Not sure if this is intentional or not but it will certainly look weird on the site. Can you fix at least the PNG so it doesn't have this?
2. Not a big deal and I would otherwise fix it myself but the raster and vector URLs are wrong. (Not sure why this can't be autopopulated but it is what it is.) Obvs see existing files for the format etc.

Thanks.