Add JSON Schema support (#3046)

## Summary

This PR adds JSON Schema support. The setup mirrors Ruff's own.

crates/uv-toolchain/src/python_version.rs

@@ -41,6 +41,17 @@ impl FromStr for PythonVersion {
     }
 }
 
+#[cfg(feature = "schemars")]
+impl schemars::JsonSchema for PythonVersion {
+    fn schema_name() -> String {
+        String::from("PythonVersion")
+    }
+
+    fn json_schema(gen: &mut schemars::gen::SchemaGenerator) -> schemars::schema::Schema {
+        <String>::json_schema(gen)
+    }
+}
+
 #[cfg(feature = "serde")]
 impl<'de> serde::Deserialize<'de> for PythonVersion {
     fn deserialize<D: serde::Deserializer<'de>>(deserializer: D) -> Result<Self, D::Error> {