<hN> refactor

[francisrupert]

Summary

Significant feedback of the Design System is the <hn> type size is proportionally too big. Quite often product teams manually override them, or worse, merely use incorrect elements to achiev the text size they visually prefer (e.g. using <h2> in place of <h1>.

Task

Propose new type sizing scale.

Possible to be done in concert with #306.

[francisrupert]

Descoped. Defer to using Text Header Utilities to appropriately manage header size and proportion while retaining hierarchy and not sacrificing usability/accessility/etc, e.g.

<h1 class="fsa-text--h2 fsa-text--h1@m">Page Tittle</h1>