[New innosetup version] is-6_6_0

[github-actions]

https://github.com/jrsoftware/issrc/releases/tag/is-6_6_0

[dscho]

I like the changes, especially the Dark Mode! But it will only be released next Monday.

[dscho]

Also, as @mjcheetham points out, the installer will need a little help before being ready for dark mode: The red (NEW!) markers (which we should really remove for things that haven't been new for a while) are sure to look awful in Dark Mode ;-)