Sidebar UI for rooms

This release adds a new sidebar UI that currently shows a single room.

Behind the scenes, the message data is reorganized a bit to accommodate messages going to different rooms. That reorganization has to be performed manually to retain chat logs, so updating a running version of Smol Chat will not go seemlessly (thus the minor point release bump, v0.1.0).

Here is how to update the data store manually:

cd .data
mkdir rooms
mv messages rooms/commons
echo '{"dirs": ["commons"]}' > rooms/.index.json