fix: Correct namespace closure for AddGroup in group.hpp

Author: weilycoder

weilycoder/ds/group.hpp

@@ -1,6 +1,7 @@
 #ifndef WEILYCODER_GROUP_HPP
 #define WEILYCODER_GROUP_HPP
 
+namespace weilycoder {
 /**
  * @brief Additive Group
  * @tparam T Type of the elements
@@ -11,5 +12,6 @@ template <typename T> struct AddGroup {
   static constexpr T identity() { return T{}; }
   static constexpr T inverse(const T &a) { return -a; }
 };
+} // namespace weilycoder
 
 #endif