Expose `vis.timeline.Core` for customization purposes (see #1126)

HISTORY.md

@@ -16,6 +16,7 @@ http://visjs.org
 ### Timeline
 
 - Implemented option `multiselectPerGroup`. Thanks @hansmaulwurf23.
+- Expose `vis.timeline.Core` for customization purposes.
 
 ### Graph2d
 

index.js

@@ -22,8 +22,9 @@ exports.graph3d = {
 exports.Timeline = require('./lib/timeline/Timeline');
 exports.Graph2d = require('./lib/timeline/Graph2d');
 exports.timeline = {
-  DateUtil: require('./lib/timeline/DateUtil'),
+  Core: require('./lib/timeline/Core'),
   DataStep: require('./lib/timeline/DataStep'),
+  DateUtil: require('./lib/timeline/DateUtil'),
   Range: require('./lib/timeline/Range'),
   stack: require('./lib/timeline/Stack'),
   TimeStep: require('./lib/timeline/TimeStep'),
@@ -37,13 +38,13 @@ exports.timeline = {
       RangeItem: require('./lib/timeline/component/item/RangeItem')
     },
 
+    BackgroundGroup: require('./lib/timeline/component/BackgroundGroup'),
     Component: require('./lib/timeline/component/Component'),
     CurrentTime: require('./lib/timeline/component/CurrentTime'),
     CustomTime: require('./lib/timeline/component/CustomTime'),
     DataAxis: require('./lib/timeline/component/DataAxis'),
     GraphGroup: require('./lib/timeline/component/GraphGroup'),
     Group: require('./lib/timeline/component/Group'),
-    BackgroundGroup: require('./lib/timeline/component/BackgroundGroup'),
     ItemSet: require('./lib/timeline/component/ItemSet'),
     Legend: require('./lib/timeline/component/Legend'),
     LineGraph: require('./lib/timeline/component/LineGraph'),