fix: Added missing enum tuple variant check and error

tests/ui/tuple_enum_variant.rs

@@ -0,0 +1,12 @@
+use lua_typed::Typed;
+
+#[derive(Typed)]
+#[serde(tag = "tag")]
+enum Test {
+    A,
+    B(String),
+    C(u8),
+    D { test: f32 },
+}
+
+fn main() {}

tests/ui/tuple_enum_variant.stderr

@@ -0,0 +1,11 @@
+error: Tuple structs/variants are currently not supported by Typed
+ --> tests/ui/tuple_enum_variant.rs:7:6
+  |
+7 |     B(String),
+  |      ^^^^^^^^
+
+error: Tuple structs/variants are currently not supported by Typed
+ --> tests/ui/tuple_enum_variant.rs:8:6
+  |
+8 |     C(u8),
+  |      ^^^^

tests/ui/tuple_struct.stderr

@@ -1,4 +1,4 @@
-error: Tuple structs are not supported by Typed
+error: Tuple structs/variants are currently not supported by Typed
  --> tests/ui/tuple_struct.rs:4:16
   |
 4 | pub struct Test(u8);