Merge branch 'feature/parser_performance' into develop

- improved parser performance by avoiding a copy of the result value
diff --git a/src/json.hpp b/src/json.hpp
index 4d5e9dd..d08ad58 100644
--- a/src/json.hpp
+++ b/src/json.hpp
@@ -8485,7 +8485,7 @@
 
             // return parser result and replace it with null in case the
             // top-level value was discarded by the callback function
-            return result.is_discarded() ? basic_json() : result;
+            return result.is_discarded() ? basic_json() : std::move(result);
         }
 
       private:
diff --git a/src/json.hpp.re2c b/src/json.hpp.re2c
index 7441e29..0aadde9 100644
--- a/src/json.hpp.re2c
+++ b/src/json.hpp.re2c
@@ -7795,7 +7795,7 @@
 
             // return parser result and replace it with null in case the
             // top-level value was discarded by the callback function
-            return result.is_discarded() ? basic_json() : result;
+            return result.is_discarded() ? basic_json() : std::move(result);
         }
 
       private: