Trigger stickyChange when attaching viewport (#129)

- Fixes an issue in chromium browsers where:
-- If the table has a sticky header and stickyPositions is not yet initialized
-- And a scrollToIndex is issued to an index outside the current range
-- The browser triggers a second scroll event when initializing the sticky elements, possibly messing up the scrolling and not showing the index issued to scrollToIndex

projects/ng-table-virtual-scroll/src/lib/fixed-size-table-virtual-scroll-strategy.ts

@@ -40,6 +40,7 @@ export class FixedSizeTableVirtualScrollStrategy implements VirtualScrollStrateg
   public attach(viewport: CdkVirtualScrollViewport): void {
     this.viewport = viewport;
     this.viewport.renderedRangeStream.subscribe(this.renderedRangeStream);
+    this.stickyChange.next(0);
     this.onDataLengthChanged();
   }