Set additional CPACK variables for RPM generator

Sets the following when querying the generated RPM's info:

Group       : System Environment/Libraries
License     : MIT
URL         : https://github.com/gabime/spdlog
Summary     : Fast C++ logging library
Description :
Very fast, header-only/compiled, C++ logging library.

cmake/spdlogCPack.cmake

@@ -14,6 +14,7 @@ set(CPACK_INSTALL_CMAKE_PROJECTS
 set(CPACK_PROJECT_URL "https://github.com/gabime/spdlog")
 set(CPACK_PACKAGE_VENDOR "Gabi Melman")
 set(CPACK_PACKAGE_CONTACT "Gabi Melman <gmelman1@gmail.com>")
+set(CPACK_PACKAGE_DESCRIPTION_SUMMARY "Fast C++ logging library")
 set(CPACK_PACKAGE_VERSION_MAJOR ${PROJECT_VERSION_MAJOR})
 set(CPACK_PACKAGE_VERSION_MINOR ${PROJECT_VERSION_MINOR})
 set(CPACK_PACKAGE_VERSION_PATCH ${PROJECT_VERSION_PATCH})
@@ -23,4 +24,9 @@ if (PROJECT_VERSION_TWEAK)
 endif ()
 set(CPACK_PACKAGE_RELOCATABLE ON)
 
+set(CPACK_RPM_PACKAGE_LICENSE "MIT")
+set(CPACK_RPM_PACKAGE_GROUP "System Environment/Libraries")
+set(CPACK_RPM_PACKAGE_URL ${CPACK_PROJECT_URL})
+set(CPACK_RPM_PACKAGE_DESCRIPTION "Very fast, header-only/compiled, C++ logging library.")
+
 include(CPack)