Add react update guide from 18.9.0 to 19.0.0

[mddragnev]

Closing #1496

[dkamburov]

@mddragnev A few more stuffs we need to mention:

• The IgrDataGrid is now in another package igniteui-react-data-grids, which makes the igniteui-react-grid package lightweight:

  • before import { IgrDataGrid } from 'igniteui-react-grids';
  • now import { IgrDataGrid } from 'igniteui-react-data-grids';

• The key prop is no longer required for columns or child components of the grid

• There were types that were exposed as classes, which is no longer the case. One example - IgrPivotConfiguration
  -before const pivotConfiguration1 = new IgrPivotConfiguration();
  -now let pivotConfiguration1: IgrPivotConfiguration = {rows:[], columns:[], values:[]};
  

[mddragnev]

@dkamburov
For the key part I have already added a point:
- Ignite UI for React components no longer require a ***key*** property, unless it is necessary according to React`s [documentation](https://react.dev/learn/rendering-lists#keeping-list-items-in-order-with-key)
The other two I will add.