Implemented notifications with SwayNotificationCenter, as well as theming using
the custom theme module. Some Waybar code had to be updated too, and was
also simplified in order to be more consistent with the new
SwayNotificationCenter implementation.
I decided to refactor how the theme module works. The idea is, that I
wanted originally a module that I could give a base16 scheme name to,
and use that globally in my config. However, scheme only took the base16
scheme name without any checks, which was pretty bad. I ended up
creating a new option, schemeName, that scheme is computed from. It then
makes the whole configuration cleaner, and avoids long inputs
interpolations with the scheme name.
