Add a formatting toolbar to Composer which appears when selecting text. It’s
enabled by default in the default components and can also be custom built with
new primitives (Composer.FloatingToolbar and Composer.MarkToggle) and new
APIs (const { marks, toggleMark } = useComposer()).
Add new --lb-line-height token to control the line height of main elements
(e.g. comment bodies in comments and composers).
Remove Timestamp export mistakenly added to @liveblocks/react-ui, it
should be imported from @liveblocks/react-ui/primitives instead.
