More run properties

Built on #18 -- relevant commits starting with 942528a

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  - [x] Add complex script bold
  - [ ] Add directional override
  - [ ] Add text border
  - [ ] Add caps
  - [ ] Add color
  - [ ] Add complex script formatting
  - [ ] Add bidirectional embedding level
  - [ ] Add double strikethrough
  - [ ] Add East Asian typography settings
  - [ ] Add animated text effect
  - [ ] Add emphasis
  - [ ] Add embossing
  - [ ] Add manual run width
  - [ ] Add text highlighting
  - [ ] Add complex script italics
  - [ ] Add imprinting
  - [ ] Add kerning
  - [ ] Add run-level language settings
  - [ ] Add no-proof setting
  - [ ] Add math container
  - [ ] Add outline
  - [ ] Add vertical position
  - [ ] Add run-level fonts
  - [ ] Add run-level styles
  - [ ] Add right-to-left flag
  - [ ] Add shadow
  - [ ] Add shading
  - [ ] Add small caps
  - [ ] Add snap to grid
  - [ ] Add spacing
  - [ ] Add spec vanish
  - [ ] Add single strikethrough
  - [ ] Add font size
  - [ ] Add complex script font size
  - [ ] Add underline
  - [ ] Add hidden text
  - [ ] Add vertical alignment
  - [ ] Add expanded / compressed text
  - [ ] Add web hidden text