Add supporting themes required for Lotusdocs

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

@@ -0,0 +1,8 @@
+// @flow
+import { type BasePlacement, type Placement, auto } from '../enums';
+
+export default function getBasePlacement(
+  placement: Placement | typeof auto
+): BasePlacement {
+  return (placement.split('-')[0]: any);
+}