Add a replacement for `gtk_file_chooser_add_choice()`
gtk_file_chooser_add_choice() was deprecated with no replacement.
I have a use case where I want the user to specify the MIDI file format (there are 3 types: Format0/Format1/Format2) when saving MIDI files. This is similar to having a choice for "text encoding" or other similar file format options in other apps. According to @ebassi , "a couple of apps (gnome-text-editor and gnome-builder, mainly) have expressed it as a requirement for loading text files with a specific encoding".