Subheader

[Jon Winton]

Editing

• Allow users to select between the three different font sizes
• though the user-facing interface would only display as s/m/l.
• it would have s/m/l options that would correspond to specific font and line-heights.
• An id for each element should be computed from the text value so we can handle linking to individual sections. Follow GitHub's pattern for this id generation but also allow users to define their own value for this id