Add SupportImageTypes

[Wlhet]

Can you add support image type > ".emf"

xmlDrawing.go
line 121
supportImageTypes = map[string]string{".gif": ".gif", ".jpg": ".jpeg", ".jpeg": ".jpeg", ".png": ".png", ".tif": ".tiff", ".tiff": ".tiff"}

supportImageTypes = map[string]string{".gif": ".gif", ".jpg": ".jpeg", ".jpeg": ".jpeg", ".png": ".png", ".tif": ".tiff", ".tiff": ".tiff", ".emf": ".emf"}

[xuri]

Thanks for your issue. I have added support for allowing insert EMF format images. Please upgrade to the master branch code. This feature will be released in the next version, and note that you need to use a specified third-part or custom image decoder and encoder.

[Wlhet]

Thank you very much.