Extract ATLAS styling and utility function in another package

[VaiTon]

trafficstars

It could be useful to create Makie graphs for the ATLAS collaboration. In particular:

• ATLASTHEME
• collabtext!

[Moelf]

in principle yes, right now they don't add extra dependencies and there aren't many of them. If we get more real users of these and people start contributing stuff I'd certainly isolate them