Support for Markdown in Fountain files

[aako]

I'm trying to get headline folding working in Fountain files. I added the following keybinding to my User Keymap file and the console says it activates the smart_folding command but it doesn't fold the text and it just inserts a tab character. So there must be some code in smart_folding.py that prevents it from running on Fountain files. It would be cool to just get this working on my own.

{ "keys": ["tab"], "command": "smart_folding", "context":
        [
            { "key": "selector", "operator": "equal", "operand": "markup.section.fountain" }
        ]
    }