Information/notification message when a story uses an outdated version of a format

[webbedspace]

Regarding #1299: I think, when you edit a story built in old versions of existing formats, something should appear informing authors of this, who might simply assume that the story is using the current format and try to use cutting-edge features.

My idea is: imagine a thin strip at the top of the story map, in a neutral colour like blue or purple, below the top menu bar, with a message reading something like "This story currently uses . The current version of is <version number 2>." It would vanish after 10 seconds or if the user clicks the X at the far right.

I was going to add something like this to Harlowe's syntax highlighter, but I think all formats would benefit from this feature. Plus, that feels like the wrong place to put a notification like this.

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[klembot]

This could be something we put into the story list. I'm reluctant to pop an alert at a user because they may be well aware of newer story format versions and are not ready to upgrade, e.g. they don't want to deal with backward incompatibilities in a story they've been working on for a long time. And tracking notifications so the user doesn't see repeated ones adds a lot of implementation complexity.