Support Date Range data type

Motivation

Excel files support basic/primitive data types. However, most would include something like a start date and end date type of data. In Drupal, this is mostly handled by the Date Range core module. It would be great if the Excel Importer was able to detect such fields and supply the appropriate data and structure when creating a node with Date Range fields.

Proposed resolution

When trying to get the correct value to pass to the node creation code, detect the field type and if it's a type of "daterange" supply an array of the following structure:

[ 
   "value" => "2020-11-18T12:00:00", 
   "end_value" => "2020-11-28T12:00:00"
]