Added support for headerRowClass.

[Agent009]

Works similar to rowClass but gets applied on the header row.

<DataGrid ... rowClass={rowClass} headerRowClass={headerRowClass} />

[amanmahajan7]

Can we not target header row with a grid class?

<DataGrid className="custom-header" ... />

.custom-header > .rdg-header-row {
  ...
}

[Agent009]

Can we not target header row with a grid class?

<DataGrid className="custom-header" ... />

.custom-header > .rdg-header-row {
  ...
}

Can do, but that doesn't allow for using pre-defined classes from other systems such as Tailwind. The dedicated property was added to cater for this.