Accept file extension rmdoc

[qwert2003]

The web interface of reMarkable device software 3.10 lets export a notebook as an archive file with the suffix rmdoc.
The resulting file is a zip archive (suffix .rmdoc) with the notebook data. It seems to be the same content as when using rmapi to download (suffix .zip).
If I download a notebook.rmdoc using the web interface and rename it to notebook.zip I can upload the file using rmapi.

Thus rmapi put could accept archive files with the extension .rmdoc:
rmapi put notebook.rmdoc