Define Grommet theme font sizes in rem & line-height in unitless numbers

[goplayoutside3]

Package

lib-grommet-theme

Is your feature request related to a problem? Please describe.

To increase platform-wide accessibility we should define our font sizes in rem units rather than hardcoded pixels. It's also preferred to define line-height as a unitless ratio rather than pixels.

Describe the solution you'd like

The size (font-size) prop in our Grommet theme components should be redefined for paragraphs, text, and headings. Each are linked below, and also have a height prop which corresponds to line-height.

Paragraphs

front-end-monorepo/packages/lib-grommet-theme/src/index.js

Line 466 in d9856fb

paragraph: {

Text

front-end-monorepo/packages/lib-grommet-theme/src/index.js

Line 523 in d9856fb

text: {

Headings

front-end-monorepo/packages/lib-grommet-theme/src/index.js

Line 309 in d9856fb

heading: { // medium is the default

Additional context

Building upon #6007

Related to: #5469