CMake and pkg-config files should be installed into architecture-agnostic directories #59
Description
Environment
toml++ version and/or commit hash: bf26a88
Describe the bug
CMake and pkg-config files are installed into architecture-specific directories despite the library being header-only and thus always architecture-agnostic.
CMake files should go into /usr/lib/cmake/tomlplusplus, pkg-config into /usr/share/pkgconfig.