Add documentation about excel template reports with jxls

[metas-rc]

Please, put the content of this message in a documentation file : https://github.com/metasfresh/me03/issues/16163#issuecomment-1695841844

Target audience for the documentation: metasfresh devs

[metas-Kay]

Added new section "Excel Report Templates (Jxls)" to Application Dictionary Guide.

• How to add columns to an Excel template
• How to protect and unprotect Excel sheets with a password
• How to make a cell read-only in an Excel sheet (lock cell)
• How to hide entire columns in an Excel sheet