refactor: Fix typo of namespace in src code

Author: FrozenLemonTee

src/primitives/primitive.impl.cppm

@@ -10,6 +10,8 @@ export namespace mcpplibs::primitives {
 
 template <typename T, primitive::policy::policy_type... Policies>
 struct primitive {
+template <underlying_type T,
+          policy::policy_type... Policies>
 template <underlying_type T,
           policy::policy_type... Policies>
   using value_type = T;