[ADF-4122] Add sticky header feature to datatable and refactor styles (#4370)

* [ADF-4122] Add sticky header config to datatable and refactor styles

* [ADF-4122] Fix core unit tests

* [ADF-4122] Commit requested changes

* [ADF-4122] Fix e2e tests

* Update docs/core/datatable.component.md

Co-Authored-By: davidcanonieto <david.cano@alfresco.com>

lib/core/datatable/components/datatable/datatable.component.ts

@@ -119,6 +119,10 @@ export class DataTableComponent implements AfterContentInit, OnChanges, DoCheck,
     @Input()
     showHeader: boolean = true;
 
+    /** Toggles the sticky header mode. */
+    @Input()
+    stickyHeader: boolean = false;
+
     /** Emitted when the user clicks a row. */
     @Output()
     rowClick = new EventEmitter<DataRowEvent>();