table support (worksheet/tableParts and table)

[ArthurDumas]

I just started using excel4node and it is a terrific library!

My feature request is to add table support as defined here:

• https://docs.microsoft.com/en-us/office/open-xml/working-with-tables
• https://docs.microsoft.com/en-us/dotnet/api/documentformat.openxml.spreadsheet.tableparts?view=openxml-2.8.1
• https://docs.microsoft.com/en-us/dotnet/api/documentformat.openxml.spreadsheet.table?view=openxml-2.8.1

I did a folder compare on the xlsx content for a simple example with and without a single table on a single worksheet.

The worksheet root element has a tableParts element which has a tablePart element. There is a new xml file in the "tables" folder with root element table.