Allow to forward messages with images to media channels

[Alathreon]

Is your feature request related to a problem? Please describe.

A media channel is a channel where you can only send messages with images.
But currently, if you use the new forward feature to forward a message with an image, i will fail, it won't notice the image.

Describe the solution you'd like

Allow to forward messages that contain an image to media channels.

Describe alternatives you've considered

Ignore the problem. Since it's niche, because you could copy an image instead, this issue could be ignored.

Additional context

https://support.discord.com/hc/en-us/articles/24640649961367-Message-Forwarding

[billpapat]

Would like to work on it.