feat(CustomizationService):Add a customization service (#2984)

* feat(customization):Add a customization service

Update UICustomizationService to v3-stable.

Also, adds an example customization for tab colors

* moved the customization service to ui category

platform/viewer/public/config/default.js

@@ -3,6 +3,10 @@ window.config = {
   // whiteLabelling: {},
   extensions: [],
   modes: [],
+  customizationService: {
+    // Shows a custom route -access via http://localhost:3000/custom
+    // helloPage: '@ohif/extension-default.customizationModule.helloPage',
+  },
   showStudyList: true,
   maxNumberOfWebWorkers: 4,
   // below flag is for performance reasons, but it might not work for all servers