CSV Parser 2.2.1

This is a simple CMake change that makes it easier to #include "csv.hpp" in a CMake project that grabs csv-parser using FetchContent_Declare().

What's Changed

• Provide directory of library's header as the include directory by @grosscol in #220

New Contributors

• @grosscol made their first contribution in #220

Full Changelog: 2.2.0...2.2.1