title: In the development of a Firefox Add-on, how would I create a new "about:" page if it is possible?
body: <p>I have made a small extension for Google Chrome and I would like to port it over to Firefox. However, it appears that the first thing my extension does in Chrome (replaces the new tab page with my custom page) is not allowed in Firefox anymore. So I was wondering if I could create and "about:apod" page that would load my plugin content. If not, how can I make this plugin visible in Firefox?</p>
  
  <p>Manifest (Chrome):</p>
  
  <pre><code>{
    "manifest_version": 2,
    "name": "NASA APOD Home Page",
      "chrome_url_overrides" : {
      "newtab": "index.html"
    },
    "permissions": [
          "https://api.nasa.gov/*"
      ],
    "version": "0.1"
  }
  </code></pre>
  
  <p>Then, it makes my index.html the "newtab" page:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
  
      &lt;head&gt;
          &lt;title&gt;APOD&lt;/title&gt;
          &lt;script type="text/javascript" src="jquery-3.2.1.js"&gt;&lt;/script&gt;
          &lt;script type="text/javascript" src="main.js"&gt;&lt;/script&gt;
          &lt;link rel="stylesheet" type="text/css" href="style.css"&gt;
          &lt;link rel="stylesheet" href="https://cdn.linearicons.com/free/1.0.0/icon-font.min.css"&gt;
      &lt;/head&gt;
  
      &lt;body&gt;
          &lt;div id="info"&gt;
              &lt;span id="time"&gt;&lt;/span&gt;
              &lt;span id="title"&gt;&lt;/span&gt;
              &lt;span id="desc_expand" class="lnr lnr-chevron-up"&gt;&lt;/span&gt;
              &lt;span id="desc"&gt;&lt;/span&gt;
          &lt;/div&gt;
      &lt;/body&gt;
  
  &lt;/html&gt;
  </code></pre>