parse_inflection doesn't support kebab-case

[pauliesnug]

When using specta with serde the following code raises the error: specta: found string literal containing an unsupported inflection at "kebab-case".

#[derive(specta::Type, Serialize, Deserialize, Debug)]
#[serde(rename_all = "kebab-case")]
pub enum MyEnum { Unknown, OtherThing }

https://github.com/oscartbeaumont/specta/blob/main/macros/src/utils.rs#L90