Fix: Add `ejs` to Prism language configuration

[JoshDevHub]

Because

Code examples using ejs weren't being given proper syntax highlighting.

This PR

• adds "ejs" to the languages array in the configuration for Prism (the library used to provide syntax highlighting).

Issue

Closes #4497

Additional Information

Pull Request Requirements

• [x] I have thoroughly read and understand The Odin Project Contributing Guide
• [x] The title of this PR follows the keyword: brief description of change format, using one of the following keywords:
  • Feature - adds new or amends existing user-facing behavior
  • Chore - changes that have no user-facing value, refactors, dependency bumps, etc
  • Fix - bug fixes
• [x] The Because section summarizes the reason for this PR
• [x] The This PR section has a bullet point list describing the changes in this PR
• [x] I have verified all tests and linters pass after making these changes.
• [x] If this PR addresses an open issue, it is linked in the Issue section
• [ ] If applicable, this PR includes new or updated automated tests

[JoshDevHub]

To QA:

1. Visit the preview tool in the review app (the path is /lessons/preview)

2. Paste this code in. Fence it with triple backticks and add the language ejs after the opening set of backticks:

   <nav>
   <ul>
    <% for (let i = 0; i < links.length; i++) { %>
      <li>
        <a href="<%= links[i].href %>">
          <span> <%= links[i].text %> </span>
        </a>
      </li>
    <% } %>
   </ul>
   </nav>

   3. Preview the markup and confirm that there's highlighting.

   Here's what it currently looks like on main for comparison: