Provide hovers and placeholder text #1932
Description
Summary
Add hovertext to UI elements to describe their intended use. Add helpful placeholder text to search boxes.
Expected Behaviour
For example, the main search bar could have a grey placeholder like "Search titles, descriptions, pids, etc". The hovertext could be something like "Free-text search over all top-level dataset fields. Scientific Metadata are not searched." (or whatever the correct description of our search is).