CI builds of Steamworks SDK for CMake build systems

PLEASE NOTE: Choose the relative version tag before using CMake files as they will be updated to reflect each version needs!

See cmake folder for include files. Then in your own library CMakeLists.txt do:

find_package(SteamworksSDK REQUIRED)

...

target_link_libraries(<libname>
  ...
  # Link the SDK
  SteamworksSDK::SteamworksSDK
  # Link the AppTicket
  SteamworksSDK::AppTicket
  ...
)

SDK documentation can be found here: https://partner.steamgames.com/doc/sdk