Add support for .msg (and other) attachments to Survey123

[LindsayRaabe_FPCWA]

Simple idea - add support for more file types to Survey123 (ArcGIS Online) to support relevant documentation collection for things like incident reporting forms. We've just discovered that emails (.msg) and other file types (discussed here and documented here) aren't accepted so would need to be converted to PDF's first or Zipped. 

[MarttiVaali1]

Yes! Also support for gpx files would be good to have.