New text formats

Hi,

Many thanks for this great plugin.
I would like to add to extension: .ris and .bib which are simple text files (bibliographic references).

For the MIME i use text/plain.

I ticked the 2 boxes at the top of the settings page:
to be used only if you are unable to upload files you have enabled by selecting their type….

but the new formats do not appear in the list and I cannot upload any file featuring this format. Your Help would be greatly appreciated. Do I need to do alter any configuration file on the server?

Many thanks.

Georges