Use rem units for typography

[robinmetral]

Closes #1679

Purpose

Switches typography units to rem, for accessibility reasons.

This change will ensure that text scales based on user font size settings.

This is a major (therefore targeting next) because apps will need to make sure they're not changing the default rem value (it should be 16px).

This is how the Storybook looks when making font size "very large" on Chrome:

Before (prod)	After (preview)

Approach and changes

• update typography design tokens
• use design tokens in Badge component (unsure why it was hardcoding typography values before)
• update snapshots (this is the bulk of the diff)

Definition of done

• Development completed
• Reviewers assigned
• Unit and integration tests
• Meets minimum browser support
• Meets accessibility requirements

[sumup-clark]

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[changeset-bot]

🦋 Changeset detected

Latest commit: ecbd4cd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
@sumup/circuit-ui	Major
@sumup/design-tokens	Major

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[vercel]

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Name	Status	Preview	Updated
oss-circuit-ui	✅ Ready (Inspect)	Visit Preview	Sep 22, 2022 at 4:17PM (UTC)

[codecov]

Codecov Report

Merging #1760 (ecbd4cd) into next (b03da80) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             next    #1760   +/-   ##
=======================================
  Coverage   91.60%   91.60%           
=======================================
  Files         172      172           
  Lines        3526     3526           
  Branches     1177     1173    -4     
=======================================
  Hits         3230     3230           
  Misses        275      275           
  Partials       21       21           

Impacted Files	Coverage Δ
packages/circuit-ui/components/Badge/Badge.tsx	100.00% <ø> (ø)
packages/design-tokens/themes/shared.ts	0.00% <ø> (ø)