Procfile has no extension so it doesn't associate with an app?

This is just a small annoyance but the Heroku Procfile does not have an extension. This causes me to have to select an application for it, each time I double click it.

Normally after selecting an application for a file, the system remembers and I don't have to do it again.

I'm wondering if I can just add a random extension and it will still work?

Something like

Procfile.procfile

or

Procfile.txt

Also because it has no extension there is no icon associated with it as well if this is not obvious.