"did you mean <>?" for the unknown rule diagnostic

[a-frantz]

Diagnostic invoked here.

If a user has a comment that reads #@ except: SnackCase we should suggest did you mean 'SnakeCase'?. The logic for determining the nearest rule should be exposed such that it can be accessed by sprocket (so that sprocket can make similar suggestions for typos on the lint --except <> command line).

As part of this I also suggest we "upgrade" the current diagnostic into a full-fledged Rule that can be disabled. A pretty niche application, but there is a use case for this disabling. Imagine a user needs to run sprocket vX in one environment and sprocket vY in another. vY has a rule (FooRule) not implemented in vX. The lint directive #@ except: FooRule would currently cause a diagnostic when running vX. There is currently no way to prevent that diagnostic from being emitted.
I think the user should be able to write #@ except: UnknownRule,FooRule to get their desired behavior (no diagnostics emitted under either version).