feature: font settings for chinese characters

[apttx]

characters can be hard to read for learners. and matching different fonts makes it even harder.

• size
  • dropdown with values:
    • small
    • medium (= current size, initial value)
    • large
  • apply to:
    • list item
    • flashcards
  • coordinate with feature: add option to also show other character set if different #92, possibly create a shared component for this
• font type
  • dropdown with values:
    • modern or display (= current font)
    • brush strokes or paper; a font closer to what's often used, like the svgs in https://github.com/skishore/makemeahanzi (feature: integrate the insanely awesome makemeahanzi #78). debate whether brush strokes is a good name