In PR #378 ("container: Allow converting more document formats"), we
added support for the following MIME types:
* application/zip
* application/octet-stream
* application/x-ole-storage
* application/vnd.oasis.opendocument.spreadsheet-template
* application/vnd.oasis.opendocument.text-template
However, we forgot to add some tests for these MIME types in the repo.
In this commit, we add a file for each of these MIME types, to make sure
we have no regressions in the future.
