Previously, we stopped propagation on mousedown events to prevent
certain cases where focus was being lost after double clicking to select
a word.
Unfortunately, this also broke the ability to focus the editor by
clicking it. When investigating this, I noticed that whenever we lost
focus, the target of the mousedown event was always the cursor. So I
tried setting `pointer-events: none` on cursors and can no longer
reproduce the double-click issue.
/cc @probablycorey
fe3ea229a2