Improve Select doc

[glebfox]

Existing page: https://docs.jmix.io/jmix/flow-ui/vc/components/select.html

1. Handlers.

   1. Add renderer
   2. Add textRenderer

2. Add prefix in Elements section

3. Add css, ariaLabel, ariaLabelBy, focusShortcut, overlayClass common attributes

4. Add examples:

   1. emptySelectionCaption
   2. ItemLabelGenerator
   3. Renderer with components

5. Add Style variants description and examples: See Vaadin doc