Rustdoc should note default-feature in item descriptions

[sinistersnare]

Currently, if an item is feature-gated (Such as Axum's Query struct), it is noted at the top. That is awesome! However, the Query struct is available by default, as the query feature is a Cargo default-feature. This is confusing wording IMO.

I think that if that feature is marked as a default feature, that should be noted too. As is the wording: "Available on crate feature FEATURE only." implies it wont work by default.

[RodBurman]

Agreed it would be clearer in these cases for the documentation to say something like: "Available on crate feature FEATURE only. Feature FEATURE is enabled by default."; thus highlighting that configuration changes are only required if the user wants to disable the feature for some reason.