Add support of new React version

[A-gambit]

Here:

• update react, react-dom, @types/react, @types/react-dom, typescript versions in examples;
• update React lifecycle methods componentWillReceiveProps (to UNSAFE_componentWillReceiveProps), componentWillMount (UNSAFE_componentWillMount).
• resolve an issue with using of ref forwarding. Add the ability to use forwardRef prop in Focal elements.