chat creation issues

[r10s]

• during channel creation, it should be possible to set an image
• for group/channel creation should be possible to set a description
• when not entering a channel name, there is no padding between error message and button

[WofWca]

I think the latter should be solved by using native error messages by applying the required prop. Although I believe that does not allow for custom styles.

[nicodh]

closed with #6314