Expandable/Collapsible reply previews with an initial height limit #756
Description
Currently there is no limit on the content of a ReplyPreview, meaning that super long messages are shown in full above any message that is replying to them. Obviously this isn't ideal.
Now that Makepad supports multiple layout size parameters including min/max heights, we can easily improve this with a simple widget wrapper that limits the ReplyPreview to an initial max height, e.g., 200 pixels.
In addition, that wrapper widget should allow expanding the view to show the full reply upon a click. A nice visual effect would be a fade out towards the bottom of the reply preview, while an "Expand Preview" button fades in as an overlay above it.
We likely also want to use this wrapper for the replying-to message preview (at the top of the RoomInputBar when you're drafting a reply to a message), such that the replying-to preview doesn't take up too much screen space.