add ability for std::string in args.get<T>

include/blt/parse/argparse.h

@@ -341,6 +341,9 @@ namespace blt
                     template<typename T>
                     inline T get(const std::string& key)
                     {
+                        if constexpr (std::is_same_v<T, std::string>)
+                            return blt::arg_parse::get<T>(data[key]);
+                        else
                             return blt::arg_parse::get_cast<T>(data[key]);
                     }