The utilities-headings module defines font sizes for heading-related
helper classes. These are class-based equivalents of our regular h1–6 rules.
$ npm install --save-dev aleut.utilities.headings
<span class="u-alpha">Text in h1-size</span>
<h3 class="u-beta">Text in h2-size</h3>
<h1 class="u-gamma">Text in h3-size</h1>
<span class="u-delta">Text in h4-size</span>
<span class="u-epsilon">Text in h5-size</span>
<h4 class="u-zeta">Text in h5-size</h4>