closes https://github.com/TryGhost/Team/issues/1318
The `{{if this.members.length "" "hidden"}}` class meant that whenever loading occurred the search input was briefly changed to `display: none` which caused focus to be lost making searching rather painful. It also meant the search input disappeared completely when no members matched a search.
- switched to a standard `<input>` element to get better event handling ergonomics
- added `searchIsFocused` tracked property that is set to `true` any time the search input has focus - works around an unexpected re-render when clearing the search input whilst it has focus
- switched the "hide" conditional to a getter that takes members length, search param text, and search input focus into account so there are no unexpected hides of the search bar
bf9bbc3aa6