Add supporting themes required for Lotusdocs

themes/hugo-mod-jslibs-dist/popperjs/package/lib/utils/getOppositeVariationPlacement.js.flow

@@ -0,0 +1,10 @@
+// @flow
+import type { Placement } from '../enums';
+
+const hash = { start: 'end', end: 'start' };
+
+export default function getOppositeVariationPlacement(
+  placement: Placement
+): Placement {
+  return (placement.replace(/start|end/g, matched => hash[matched]): any);
+}