fix(ui): ignore context menu in slider view

It doesn't make sense to allow context menu here, because the context menu will technically be on a div and not an image - there won't be any image options there.

invokeai/frontend/web/src/common/util/stopPropagation.ts

@@ -1,3 +1,7 @@
 export const stopPropagation = (e: React.MouseEvent) => {
   e.stopPropagation();
 };
+
+export const preventDefault = (e: React.MouseEvent) => {
+  e.preventDefault();
+};