Simple vcpkg Overlay Ports Setup

The file vcpkg-configuration.json uses an existing vcpkg as the default registry; this assumes vcpkg as a git submodule. The baseline value is the commit hash of the vcpkg submodule. Update the hash as needed to reflect the actual version of the vcpkg registry you've got checked out as a submodule.

Overlay Ports

Use a directory vcpkg-overlays to contain the overlay ports; this is a sibling to the vcpkg submodule directory.

Create a subdirectory per port, with the subdirectory named after the port. This can either override a port from the default registry or it can be a new port that isn't in the default registry.