Add width & height tag in channel.image

[Kelvin]

Is your feature request related to a problem? Please describe.
Hello, I tried to add width & height tag for image, but I think currently is not possible?

<channel>
...
   <image>
      <url>https://s1.test.com/favicon.ico</url>
      <title>Test Blog Feed</title>
      <link>https://www.test.com/blog</link>
      <width>32</width>
      <height>32</height>
    </image>

Describe the solution you'd like
Open extra attribute for image width & height / enable custom tag