Create logo for Rector

Please see attached a version for consideration.

This is not really something that can be installed through this project though... Is a logo needed then?

@bbrala, that's completely up to you as the project maintainer.

The logo will be displayed in 3 places:

1. In Project Browser when the module card is displayed
2. On the project page, to the left of the main heading (the project name)
3. On the Gitlab project

Since there are no module releases, 1 doesn't apply. And, while the logo will show on the Gitlab page, since you're using Github, you'll never look at it there, so 3 isn't really relevant.

But case 2 may still be useful if you want it.

I have verified the logo from #2 meets the Project Browser requirements - file is PNG image, dimensions are 512x512, and file size is under 10K.

Moving to RTBC.