Is there really no way in Android to tell the os that a .md file is a text file?

I have a bunch of markdown files on dropbox. (and also some restructured text files). i just want to edit these with my text editor on android. but apparently there is no way to tell android that a .md file is just text? Android doesn’t maintain a mime/file type registry and a user can’t just add a mapping? without screwing around with app manifests?

Someone please point me in the right direction if there is a way to do this.