selectHelper *1.4.6*
====================
Whether to draw a "placeholder" event while the user is dragging.
Boolean/Function, *default*: `false`
**This option only applies to the agenda views.**
A value of `true` will draw a "placeholder" event while the user is dragging
(similar to what Google Calendar does for its week and day views).
A value of `false` (the default) will draw the standard highlighting over each cell.
A function can also be specified for drawing custom elements.
It will be given 2 arguments: the selection's start date and end date (Date objects).
It must return a DOM element that will be used.