Add support for Microsoft Office formats - DOCX and XLSX.

[LevSerov]

It's strange that there is no such topic here!
Is this really not interesting to anyone or does it sound too fantastic? Are the formats open?

Implementing this will be a very useful and pragmatic step, even if it doubles the distribution of the program! You can also make a special version. I think most office documents that the average user opens are small and simple in design! There is no point in running an entire office harvester over this! What you need here is a fast program that supports basic formatting elements!

You can also support LibreOffice formats (ODT, ODS).
Thanks. :)

[GitHubRulesOK]

SumatraPDF is based on MuPDF and it has very rudimentary office support so as a document handler has docX but not xlsX as you may expect. Look at the full size of LibreOffice over 12000 files ! and the years of development Apache took to get it "close" to Microsoft's own format. Office formats are not simple.
MuPDF had and dropped a pdf2docX specific ability see https://github.com/ArtifexSoftware/pdf2docx
There are still parts that do some docX handling but see https://mupdf.readthedocs.io/en/1.27.2/search.html?q=docx thus not listed

Formats
As you can tell by the name, we support reading PDF files. But that’s not all!
PDF
XPS and OpenXPS
EPUB (DRM-free 2.0, limited support for 3.0)
Mobipocket (MOBI)
FictionBook 2 (FB2)
ComicBook (CBZ and CBT)
Images (TIFF, JPEG, PNG, etc)
SVG (a limited subset only)

The open parts are not the usual problem as that is simply very bloated plain text as XML. What is usually problematic is use of Styling and graphics, some of which are very steeped in proprietary code internal to Microsoft. Same as NOT ALL PDF structures are licensed as Adobe Open License.

So at one time (not heard of since1.24 and we are at 1.28) there was an attempt and some still residual parts that are office biased

	Support for "SmartOffice" commercially licensed plugin to load office
	documents.

List of changes in MuPDF 1.24

	Error handling changes:
		You must call pdf_report_error in the final fz_catch. Any
		unreported errors will be automatically reported when a new
		error is raised, or when closing the fitz context.
	New formats:
		Read Office (XML) files! We internally open and convert
		docx/pptx/xlsx documents to HTML to allow reading the plain
		text content. The exact layout will NOT be preserved.

However note that is almost as basic as unzip the doc and convert to Notepad format.

Here is an Example WordPad on Left MuPDF on Right