Returns the URL to the User's avatar that triggered the command.
Discord adds image to message if link provided Read examples section
If a message contains only a link to an image, Discord sends only the image.
If a message has a link to an image AND some text, Discord sends both the link and the image.
To add image without posting the link use $attachment
To send link as a plain text wrap the function into graves like
$authorAvatar[Return Server Avatar Instead (yes/no, default is no)]