typescript(vx-demo): fix Polygons and Gradients import paths

packages/vx-demo/src/components/gallery.js

@@ -10,7 +10,7 @@ import Lines from './tiles/lines';
 import Bars from './tiles/bars';
 import Dots from './tiles/dots';
 import Patterns from './tiles/Patterns.tsx';
-import Gradients from './tiles/gradients';
+import Gradients from './tiles/Gradients.tsx';
 import Area from './tiles/area';
 import Stacked from './tiles/stacked';
 import MultiLine from './tiles/multiline';
@@ -40,7 +40,7 @@ import DragII from './tiles/drag-ii';
 import LinkTypes from './tiles/linkTypes';
 import Threshold from './tiles/threshold';
 import Chord from './tiles/chord';
-import Polygons from './tiles/polygons';
+import Polygons from './tiles/Polygons.tsx';
 import ZoomI from './tiles/zoom-i';
 import BrushChart from './tiles/brush';