Description

This PR completes the RTL behavior in such a way that:

1. Elements flow from right to left when rtl is set. The original Position struct has not changed, it still has a left property, which now means "horizontal start position". When in rtl, it will be the position from the right.
2. Dragging - works correctly in rtl mode. With minimal changes to the code.
3. Resizing - the same. The resize event has new properties to make it more semantic without testing for the rtl flag everywhere.

This closes the issue #819.

Checklist

• Created tests which fail without the change (if possible) - not possible, tests already fail on master
• All tests passing (yarn test) - the same tests fail on master
• Extended the README / documentation, if necessary - not necessary