Update column pinning topic for React 19

[IMinchev64]

No description provided.

[mddragnev]

Two things:

1. At the snippet showing the columnPinning event handler - could you set the argument type?
2. Pinning position is no longer a class but a type so PinningPosition should be set like this:

  const pinning: IgrPinningConfig = { columns: ColumnPinningPosition.End };