[FEATURE]: a feature of a customized keybinding

[yu2chuan]

Is your feature request related to a problem? Please describe.
a keybinding can do <u><mark>key contents</mark></u> or define a style for font or background like <span style="background-color:Blueviolet;color:white">Blueviolet</span>

Describe the solution you'd like

currently, ctrl +i and ctrl +b are good. But sometimes users still prefer a different way to highlight critial things in the notes.

Describe alternatives you've considered

Additional context

[drl990114]

Already in the development plan, I will @ you when it is released.