message: Add keys to mapped elements in value editor demo
diff: @@ -25,14 +25,16 @@ import { ValueEditor } from 'react-querybuilder';
  fieldSelector: ({ value, options }) => (
  <select value={value} disabled>
  {options.map(o => (
  - <option value={o.name}>{`valueEditorType: "${o.label}"`}</option>
  + <option key={o.name} value={o.name}>{`valueEditorType: "${o.label}"`}</option>
  ))}
  </select>
  ),
  operatorSelector: ({ value, options }) => (
  <select value={value} disabled>
  {options.map(o => (
  - <option value={o.name}>{o.label}</option>
  + <option key={o.name} value={o.name}>
  + {o.label}
  + </option>
  ))}
  </select>
  ),
  