feat: add reflection for const-only getter

include/reflection/reflection.h

@@ -57,6 +57,12 @@ public:
     const_members_.emplace(id, CONST_REFLECTION((obj.*get)()));
     return *this;
   }
+  
+  template <typename T>
+  Reflection & bind(std::string_view id, T (Obj::*get)() const) {
+    const_members_.emplace(id, CONST_REFLECTION((obj.*get)()));
+    return *this;
+  }
 
   template <typename T> Reflection & bind(std::string_view id, T Obj::*member) {
     members_.emplace(id, REFLECTION(obj.*member));