This closes #1777, fix the GetStyle or GetConditionalStyle function to returns incorrect DecimalPlaces field value

- Update documentation for the NewStyle function
- Update unit tests
- Update dependencies Go module
- Update GitHub workflow dependencies package version
- Update copyright agreement statement

- Update example code in the documentation
- Update unit tests
- Rename `PictureOptions` to `GraphicOptions`
- Adjust partial options fields data types for the `PictureOptions` and `Shape` structure
- Update dependencies module

Added two exported functions `SetWorkbookPrOptions` and `GetWorkbookPrOptions` to support setting and getting the code name property of the workbook
Re-order fields of the workbook properties group to improve the compatibility
Go Modules dependencies upgrade
Put workbook related operating in new `workbook.go` source code
Library introduction docs block updated

Fix file corrupted when save as in XLAM / XLSM / XLTM / XLTX extension in some case
New exported error ErrWorkbookExt has been added, and check file extension on save the workbook
Format source code with `gofumpt`

Rename exported constants `NameSpaceDublinCoreMetadataIntiative` to `NameSpaceDublinCoreMetadataInitiative`

Go 1.15 and later required, #65 fn: IMABS, IMCOS, IMCOSH, IMCOT, IMCSC, IMCSCH, IMEXP, IMLN and IMLOG10

typo fixed

Add different pivot options
Add header options to pivot table opts
Add Style name options to pivot table opts

workBookRelsWriter, drawingRelsWriter into relsWriter;
drawingRelsReader, workbookRelsReader, workSheetRelsReader into relsReader;
addDrawingRelationships, addSheetRelationships into addRels