add gtk4 pango markup support for clock widget

[daxcore]

hey.

adding support for Pango markup language in clock widget: https://docs.gtk.org/gtk4/method.Label.set_markup.html

i am using if for something like that in the regreet.toml:

format = "<span font='SF Pr Display Bold 52'>%A</span>\n<span font='SF Pr Display Bold 25'>%d %B</span>\n<span font='SF Pr Display Bold 12'>- %H:%M -</span>"

to get the possibility to adapt the look of ReGreet to the hyprlock theme Style-10 of https://github.com/MrVivekRajan/Hyprlock-Styles