Add option to disable autosave (not the same as #821)

Nobody has claimed this yet.

It seems that macdown saves files periodically. Issue #821 mentioned that, but focused on the "ask to save before quitting" item in System Preferences-> General. I'm talking about a file that autosaves to disk periodically, when changes haven't been saved.

Usually, this is a benefit, to prevent loss of data when the mac or the application crashes. But combine it with online editing when the file is from Box and you get a flurry of saves, each one kept in perpetuity and each one creating a separate version number(!)

So, first - am I imagining this or is there an automatic autosave going on in macdown? And if so, is there a way - short of editing offline - to prevent this from happening?

One way is to override autosave using a macdown preference. Another, better way is to autosave to a separate file and then provide a means of restoring from the file, if a crash occurs.

Start by confirming whether MacDown periodically autosaves a file edited online through Box, and compare that behavior with the macOS System Preferences > General save settings. The issue does not choose between a MacDown preference and a separate recovery file, so the desired behavior and completion criteria need clarification before implementation.

Written by the indexing model from the issue text.