allow handlebars component nesting

[cxq]

In some cases, with more complex components like media-object, we need to split them into small pieces.

Potentially, I can have several sections and that can contains "custom html" and passing everything using parameter is not flexible enough.

Here is an example with the code changes using nested templates:

{{{yield}}} is the helper that renders everything within a component helper

media-object.scss

{{#include './components/media-object/container'}}
    {{#include './components/media-object/section' align="middle"}}
        <img src="https://dummyimage.com/50x50/ededed/9b9b9b.jpg&text=IMG"/>
    {{/include}}
    {{#include './components/media-object/section'}}
        <h4>Dreams feel real while we're in them.</h4>
        <p>I'm going to improvise. Listen, there's something you should know about me... about inception. An idea is
        like a virus, resilient, highly contagious. The smallest seed of an idea can grow. It can grow to define or
        destroy you.</p>
    {{/include}}
{{/include}}

components/media-object/container.hbs

<div class="c-media-object">
    {{{yield}}}
</div>

components/media-object/section.hbs

<div class="c-media-object__section {{#if align}}c-media-object__section--{{align}}{{/if}}">
    {{{yield}}}
</div>