<issue_start><issue_comment>Title: Include subtitles and section-spacing in sample paragraphs
username_0: <img width="893" alt="Screenshot 2020-05-10 at 21 34 16" src="https://user-images.githubusercontent.com/36348559/81499360-05865d00-9306-11ea-8062-8c860fb1eddd.png">

Let the x-height to line-spacing ratio dictate all the ratios.
-  Body text and section title font sizes
-  Line-spacing and paragraph-spacing
-  Paragraph-spacing and section-spacing