Expose field name suggestions for ignored fields that are typos

[nipunn1313]

For example, if deserializing something like

[dependencies]
serde = { version = "1.0.126", optional = true, feautres = ["derive"] }

With something like

let manifest: TomlManifest = serde_ignored::deserialize(toml, |path| {
    unused.insert(format!("{}", path));
})?;

We could have serde-ignored (perhaps behind a feature flag) leverage something like lev_distance to give suggestions - which the callsite could use as suggestions

Possible new call syntax

let manifest: TomlManifest = serde_ignored::deserialize_with_suggestions(toml, 2 /* lev distance */, |path: Path, suggestions: Vec<Path>| {
    if ! suggestions.empty() {
      print("{} unused. Did you mean {}", path, suggestions[0]);
    }
    unused.insert(stringify(path));
})?;

^ which would ideally print "dependencies.serde.feautres unused. Did you mean dependencies.serde.features"

Inspired by
rust-lang/cargo#5264 and
rust-lang/cargo#9731

[nipunn1313]

I'm not sure if the idea I gave for this problem is actually achievable. In reading up, I found:

Deserializer for struct might look like this https://serde.rs/deserialize-struct.html
The wrapping deserializer in serde-ignored is passed a visitor, but can't get a list of possible valid strings that the visitor's visit_str would accept, therefore it can't augment self.path with suggestions.
I suppose it could call visitor.visit_str(guess) with a bunch of guesses of short-edit-distance, but that's hardly appetizing.

What's a better way to do this sort of thing?

[petr-tik]

i think this would be a great addition and only reinforce the rust culture of actionable error messages