API support for Charts Completed

Request for adding API support for Charts.

GemBox.Spreadsheet supports Charts only through the preservation in XLSX files.
This enables us the following scenario.
We can create an XLSX template with the desired Chart and set it up to use dynamic chart data. We can then load this XLSX template file with the GemBox.Spreadsheet and modify the data used by our Chart element. After saving these modifications in an XLSX file with the GemBox.Spreadsheet and opening a file in Excel application, we can notice that these changes are applied to our Chart element.

More information about GemBox.Spreadsheet's preservation can be found on the following link:

https://www.gemboxsoftware.com/spreadsheet/docs/preservation.html