customTime no longer accepts `options`

[barreeeiroo]

I was looking for ways to make my customTime not editable (i.e., so that users won't be dragging that item), and I came up with the following commit:

• https://github.com/visjs/vis-timeline/commit/d39a149ba0eada1fa15f40181a2b14e8e8735a23

This commit added the possibility of passing an options object so that {editable: false} would disable this drag-and-drop functionality. However, when using the library, passing this seems to have no effect. And after investigating a bit more, this change was later removed by the following commit:

• https://github.com/visjs/vis-timeline/commit/f718d3442df9a2cb1f1b890d758c77e4e369f131

Not sure if this change was intentional, but it seems like it could have been removed by mistake (no documentation highlights the opposite, and I couldn't find any discussion or issue where this removal was documented).

Are there any concerns on bringing it back?