Dynamic shared component templates with handlebars

sharedtemplates.md

Create a template that includes handlebars expressions that all the addition of classes

<!-- button.hbs -->
<a id="{{id}}" data-component="{{jsHook}}" class="c-button {{utilityClasses}} {{extensionClasses}}">
  {{text}}
</a>

You can then extend the component within your app by either adding a utility class, or by extending the component with a modifier

{{> button utilityClasses="u-pinLeft"}}

{{> button extensionClasses="c-button--my-app"}}