Update the shortcut image in web documentation

[singhay]

Image used to show how to set Quake shortcut still uses Terminix.
Please update that!!

[arcticicestudio]

This is related to the gnunn1/tilix-web repository.
I think this should be solved in #21.

[gnunn1]

I won't be able to get to this until the weekend, but as @arcticicestudio pointed out it's covered already. Additionally, note that you can simply fork the repo, create a new image and submit a PR to https://github.com/gnunn1/tilix-web