Set up periodic CI builds

[OrestZborowski-SIG]

Recently an update to a dependency caused a PR test to fail in another component. It would be useful to know of such changes earlier, so they can be addressed.

Perhaps set up a weekly CI build (one Windows + one Linux?) that ensures that the current code continues to compile and test cleanly.

This is mostly useful for riptable itself, as riptide_cpp maintains tighter compile-time dependencies.