Improve BigDecimalField doc

[KremnevDmitry]

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

1. General
   • Add Style variants description and examples: See Vaadin doc.
2. Add attributes
   • ariaLabel, ariaLabelledBy
   • css
   • focusShortcut
3. Remove attributes
   • invalid
   • requiredIndicatorVisible
4. Add elements
   • suffix
   • prefix