Add screenshot to the README.md

[Themercee]

This is more an advice. You should add some screenshot to let people know there is a UI. People loooooove nice thing 😍

[sbehrens]

Hi @Themercee,

We have a ton of screenshots on our Wiki, where you can fine our complete documentation. Take a look here to get started: https://github.com/Netflix/Scumblr/wiki/Setup-Your-First-Security-Task

I'll throw a few more screenshots in the readme as well.

[Themercee]

Yeah I look at the Wiki, but before looking I didn't know it was Web UI. I thought it was only command line on something like that! Nice work by the way