Produce release artifacts

[noelwarren]

We should add actions for tags such that we produce release build artefacts. This should be used in combination with the cmake install target.

cmake --install build --config Release --prefix install

Currently we only want to copy the headers and .cc files, but untimately we will be compiling static libs too, and we will need a different set for each msvc tool chain.
Whether we decide to go with one artefact that combines these on multiple ones is a matter of preference.