chore(*): Adding better documentation for IPinRowEventArgs.

Author: MKirova

projects/igniteui-angular/src/lib/grids/common/events.ts

@@ -119,9 +119,20 @@ export interface IRowToggleEventArgs extends IBaseEventArgs {
     cancel: boolean;
 }
 
+/**
+ * Event emitted when a row's pin state changes.
+ */
 export interface IPinRowEventArgs extends IBaseEventArgs {
-    row: IgxRowDirective<IgxGridBaseDirective & GridType>;
+    /** The row component instance, that was pinned/unpinned.
+    * May be undefined if row does not exist in the current visible data.
+    */
+    row?: IgxRowDirective<IgxGridBaseDirective & GridType>;
+    /** The ID of the row, that was pinned/unpinned.
+    *   ID is either the primaryKey value or the data record instance.
+    */
     rowID: any;
+    /** The index at which to pin the row in the pinned rows collection. */
     insertAtIndex?: number;
+    /** Whether or noy the row is pinned or unpinned. */
     isPinned: boolean;
 }