I can upload .txt, .csv and .xlsx files into the DAM, but then when editing a page, I can only find the xlsx file in the Asset Finder (left panel). I suspect this issue is around the mimetype. The files not displaying have a mimetype of text/plain and text/csv. The xlsx, which does show up, has a filetype of application/vnd.openxmlformats-officedocument.spreadsheetml.sheet.
What do I need to do for text/* mimetypes to show up in the Asset Finder?
(The reason I want to upload a csv file in particular is we are converting it to json and displaying the results in a datatable that accepts json.)