OHIF-333: Split Button (#1988)

* ohif-333: add component foundation

* ohif-333: add expandable content and mocked data

* ohif-333: improve ListMenu component for the new toolbar button and add radio behavior

* ohif-333: add click outside behavior and update primary and secondary props

* ohif-333: separate classes from markup

* ohif-333: fix layout issues

* ohif-333: extract window level component

* ohif-333: update component returns

* ohif-333: update chevron thickness

* ohif-333: remove is active prop

* Delete lerna-debug.log

* ohif-333: clean toolbar and use example in ui package

* ohif-333: update styles to avoid word break

* ohif-333: fix ui package build

Co-authored-by: Erik Ziegler <erik.sweed@gmail.com>
Co-authored-by: Danny Brown <danny.ri.brown@gmail.com>

platform/ui/index.js

@@ -65,6 +65,7 @@ export {
   Select,
   SegmentationTable,
   SidePanel,
+  SplitButton,
   StudyBrowser,
   StudyItem,
   StudyListExpandedRow,
@@ -94,6 +95,7 @@ export {
   ViewportDownloadForm,
   ViewportGrid,
   ViewportPane,
+  WindowLevelMenuItem
 } from './src/components';
 
 /** VIEWS */