Tracking completion widget issues

[isoos]

• fixing absolute positioning bug
• style change: blend with input field background
• style change: padding + rounded corners in the bottom
• style change: already typed text with different color
• display it in mini search widget (e.g. on package page)
• include the prefix in the result list
• # as a shortcut for topic: completion (also in query canonicalization)
• The list of topics takes very long to update -> prune list of suggestions