* Rename the package to `SixtyFPS-cpp-*` to make it easier to see that these are for C++
* Refer to the download and extraction process in the two C++ "READMEs"
* Set the home page url in the cmake project() command, from where cpack will pick it up for inclusion in the installer.
cc #631
The upcoming re-organization of the C++ header generation requires the
use of the CORROSION_ENVIRONMENT_VARIABLES target property, which in
turn requires CMake >= 3.19.
It does not update the version number in the README because
these are either not part of the versionized documentation
or the demantic versioning make it work anyway
This combines the tutorial sub-section from the intro (a bit weird as sub-section there)
and the usage part of the cmake section into a getting started that
has a complete little C++ example.
