Adding flexbox polyfill to IE11

Packages/ohif-compatibility/package.js

@@ -14,6 +14,7 @@ Package.onUse(function(api) {
     // Assets to be imported dynamically
     api.addAssets('public/js/svgxuse.min.js', 'client');
     api.addAssets('public/js/typedarray.js', 'client');
+    api.addAssets('public/js/flexibility.min.js', 'client');
 
     // Client imports
     api.addFiles('client/index.js', 'client');