Add a new slot for the title bar

[tibi-extera]

Is your feature request related to a problem? Please describe. I would like to style the title bar differently from the default. For example, I would like to be able to change colors, fonts, or whether there is a single button with a menu or a series of buttons. I may want to replace the title bar with a QToolbar or a QBar. At the same time, I want to limit the draggable area to the title bar, just like it is now.

Describe the solution you'd like I would like an additional slot available (suggestion: named title) that I can use to customize the title bar.