Adding Dusk as a theme

[schlick7]

Hoping you'll accept this pull request. It is only adding a theme, but I think its nice enough to share.

[jzohrab]

Thank you very much, @schlick7 ! Can you attach an image of what it looks like here? (I'm sure I'll merge it, just want to see it :-) ) Cheers!

[jzohrab]

fyi - the failed test has nothing to do with your change. (Flaky test, annoying)

[schlick7]

yes, I should have done that