Require the as prop in heading components

[connor-baer]

Purpose

A common navigation technique for users of screen reading software is jumping from heading to heading to quickly determine the content of the page. Because of this, it is important to not skip one or more heading levels. Doing so may create confusion, as the person navigating this way may be left wondering where the missing heading is.

From MDN

Approach and changes

• Made the as prop required in the Headline and SubHeadline components. This requires developers to intentionally set the heading level to ensure a consistent and accessible page structure.

Definition of done

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

[changeset-bot]

🦋 Changeset detected

Latest commit: 45efe01

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

This PR includes changesets to release 1 package

Name	Type
@sumup/circuit-ui	Major

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[codecov]

Codecov Report

Merging #1008 (45efe01) into next (23b4251) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             next    #1008   +/-   ##
=======================================
  Coverage   91.05%   91.05%           
=======================================
  Files         161      161           
  Lines        2684     2684           
  Branches      768      794   +26     
=======================================
  Hits         2444     2444           
+ Misses        215      214    -1     
- Partials       25       26    +1     

Impacted Files	Coverage Δ
...ckages/circuit-ui/components/Headline/Headline.tsx	85.71% <ø> (ø)
.../circuit-ui/components/SubHeadline/SubHeadline.tsx	100.00% <ø> (ø)
...es/circuit-ui/components/Pagination/Pagination.tsx	87.50% <0.00%> (ø)