feature request: parse org-entities-user before calling pandoc

[japhir]

Hi, great package! Love how easy it makes everything! Was very happy to see I can now easily export to docx for my colleagues who don't like good file formats.

I've started using some custom entities over the past year. See the org-mode manual for what they are. My workflow so far has been to export to latex, then export to docx with pandoc from the command line. Any way I could link this together in ox-pandoc? Or should I add the parsing to some hook? When I select the "l" option, it still has my \us{} org-entity for latex' \, and fails export (also because of missing refs).