API documentation missing image fields.

[luckydonald]

Describe the bug https://derpibooru.org/pages/api#image-response Is lacking the To Reproduce Steps to reproduce the behavior:

1. Use the API to search for *
2. Try to load the image object as documented

Expected behavior All fields are consumed when processing the ones in the documentation.

*Failing behavior Image's .size, .animated and .duration field is missing in the documentation.

Screenshots

Additional context derpi library: https://github.com/derpipy/derpi/issues/1

[luckydonald]

Would prepare a PR for you guys, but couldn't find the file for that.

[luckydonald]

Maybe something like

size	Integer	The image's file size in bytes.
animated	Boolean	Whether this image is animated.
duration	Float	Length of the animation. (Seems to always be set to `0.04` for images which aren't animated).

      <tr>
        <td><code>size</code></td>
        <td>Integer</td>
        <td>The image's file size in bytes.</td>
      </tr>
      <tr>
        <td><code>animated</code></td>
        <td>Boolean</td>
        <td>Whether this image is animated.</td>
      </tr>
      <tr>
        <td><code>duration</code></td>
        <td>Float</td>
        <td>Length of the animation. (Seems to always be set to `0.04` for images which aren't animated).</td>
      </tr>