Simply adds a `hint_text_font` (any suggestions for a better name?
hint_text_style seemed misleading as it doesn't only accept `TextStyle`)
method to the TextEdit builder that allows to set the styling
(specifically, a `FontSelection`) for the hint text.
My personal use-case for this was having body-sized hint text in a
heading-sized TextEdit, but I'm sure there's more out there.
The PR shouldn't break compatibility, as it's stored as an `Option` that
defaults to the `font_id` (which was the only behaviour prior to this)
when empty.
It looked too trivial to add something to the actual demo, but I have it
locally, so let me know if I should commit that.
Ran the check script locally, had no complaints.
ff7a3832b6