DCP-2508: Update typography

[madelinekreiff2]

What's changed (from [https://www.figma.com/file/zAayEr7SKFC0bsxKNPpIIH/%5BPDS%5D-Design-System?type=design&node-id=89%3A3004&mode=design&t=iAyc6n6cMjDn3XLJ-1] Figma)

Eyebrows:

• 14px font size, 20px line height, 1.75px letter spacing
• Various letter spacings and line heights for h1-h5
• Added h6 styles (font size variable was already there but not line height, letter spacing)
• Added p0 font size (20px body font size). These names will be changed when we implement the new typography token structure
• Medium button line height (14px font size, 20px line height)