Add honkling logo to Readme

[GantMan]

GitHub currently has four themes (75% of which are dark). One of the four themes is experimental. See them listed here:

I wanted to add your logo to your Readme, but to do so, I had to defend a transparent + black logo against dark backgrounds.

I did a simple stroke for the logo that will only show on dark themes.

This PR adds your logo to your readme in a way that works for all themes.