fix: magic_enum.hpp reference (#390)

README.md

@@ -306,7 +306,7 @@ If you like this project, please consider donating to one of the funds that help
 
 ## Integration
 
-* You should add the required file [magic_enum.hpp](include/magic_enum.hpp), and optionally other headers from [include dir](include/) or [release archive](https://github.com/Neargye/magic_enum/releases/latest). Alternatively, you can build the library with CMake.
+* You should add the required file [magic_enum.hpp](include/magic_enum/magic_enum.hpp), and optionally other headers from [include dir](include/) or [release archive](https://github.com/Neargye/magic_enum/releases/latest). Alternatively, you can build the library with CMake.
 
 * If you are using [vcpkg](https://github.com/Microsoft/vcpkg/) on your project for external dependencies, then you can use the [magic-enum package](https://github.com/microsoft/vcpkg/tree/master/ports/magic-enum).