compose: Show selectable "input chip" in place of image markdown

[chrisbobbe]

An early post-launch request:

#mobile > Change Upload behaviour @ 💬

and delete this text

Discussion is ongoing. I replied:

It's probably feasible to show a placeholder for it in the compose input, though—something like an input chip. We're not able to commit to a full WYSIWYG editor in the short-term though.

Implementation

We should look at InputChip for this.