I have been looking at Gromit if there is a function that can make a POPUP message in connection with index.html about cookies but has not found anything.
If you have a script that will take care of that, the skin allows you to plant the necessary code in the <head> section of the index and/or slide pages (the place for Javascript routines), and/or at the top or bottom of the <body> sections.
The skin itself doesn't use cookies, or collect any information from a visitor, so there's no need to build in any GDPR code. It does allow you to plug in Google Analytics, but I believe those do not run afoul of GDPR, since no user-identifiable information is collected.