[Meta] Create content for Contributor Area sections

We need to create content for all of the Contribution Areas.

Here are the guidelines for how/when/why to create a contribution area page: Guidelines for contribution areas.

For each Contribution Area page, we need to create a child issue with the following summary:

Develop/edit content for <strong>Contribute to WHATEVER IT IS</strong> Area Page of the Contributor Guide.

<h3>Tasks</h3>

For these tasks, see the following guidelines pages:
<ul>
<li><a href="https://www.drupal.org/community/contributor-guide/reference-information/guidelines-contributor-guide/areas">Guidelines for contribution areas</a></li>
<li><a href="https://www.drupal.org/community/contributor-guide/reference-information/guidelines-contributor-guide/content-types">Guidelines for Contributor Guide content types</a></li>
</ul>

Also, add comments to this issue when you do any of these tasks, explaining what you did. Tasks:

<ul>
   <li>Write or adapt content giving an overview of what happens in this contribution area. Put it into a new page under <a href="https://www.drupal.org/community/contributor-guide/contribution-areas">Contribution Areas</a>.</li>
  <li>Follow the steps in the <a href="https://www.drupal.org/community/contributor-guide/reference-information/guidelines-contributor-guide/areas">Guidelines for contribution areas</a> to get it set up properly (taxonomy term, blocks, etc.).</li>
  <li>Add related <strong>Contributor Tasks</strong>, and/or edit existing tasks to link them to this new area. A Task has a well-defined goal and well-defined steps.</li>
 <li>Add related <strong>Contributor Roles</strong>. A Role is a "position" in the community (short- or long-term).</li>
 <li>Add related <strong>Contributor Skills</strong>, if new skills are needed. A Skill gives you the knowledge to perform a Task or fill a role.</li>
 <li>If the contributor area doesn't already have strong documentation, add reference documentation in an appropriate section of the Drupal Wiki https://www.drupal.org/drupal-wiki or the Contributor Guide background section https://www.drupal.org/community/contributor-guide/reference-information.</li>
  <li>Add Contacts section to the page.</li>
</ul>

See the list of existing child issues in the sidebar of this page, to see which areas are being worked on.