Darker titlebar to match applications like terminals

[luisbocanegra]

Is your feature request related to a problem? Please describe.
Not a problem, but some window decorations like SierraBreeze[Enhanced] have an option to make titlebars match the window color, with other decorations this could be achieved by making a special color scheme and a window rule for the target application

Describe the solution you'd like
Allow specifying a list of window classess that will have a darker titlebar

How it is now on the left vs darker titlebars on the right, tell me which one looks more aesthetic 😆

Describe alternatives you've considered
Maybe requesting such feature to window decoration developers (I use Klassy), but still, not everyone use uses the same decoration

Additional context
There is a script Tkp that lets you choose a color per application basis and this feature will be ported from it