Mnemonics support

[MartinHlavna]

Hello,

having support for mnemonics (in OG tkinter underline param). Upon holding Alt key, underlined control character appears and after presssing underlined character particular menu is opened.

For example, if there is File menu section, with underline=0, F is the control character and ALT+F open file dropdown menu. Would it be possible to implement similar functionality?

[MartinHlavna]

Dug a little bit into this. in OG tkinter, in tk.Label, preceding char with \u0332 will underline it. Since CtkButton uses tk.Label internally, it should be possible to "highlight" control char.

Rest of the functionality could be implemented with bindings.