mime type in document module

Where does Documents get the mime type to be related to file?
I have files with extensions .m .nb .wl .cdf which are mapping to text/plain instead of their proper mime-types:

.nb application/vnd.wolfram.mathematica

.cdf application/vnd.wolfram.cdf.text

.m and .wl application/vnd.wolfram.mathematica.package

 

thank you,

FrancescaS