no type named 'string' in namespace 'std' after merging #249

OS: Windows 11 Pro Insider Preview Build 23536
Environment: MSYS 2 MinGW w/ Clang 16.0.5 x86_64

PR #249 added some nifty tostring methods, though `<string>` is not included in the headers and results in compilation errors (no type named 'string' in namespace 'std').