We should provide clear, step-by-step guidance here for users who want to consume beta bits.

The readme here incorrectly mentions updating the AzureVcpkg.cmake file.

https://github.com/Azure/azure-sdk-for-cpp/blob/be478542fba6091385afb2c1791eafcecf8b1ad7/README.md#getting-beta-releases-in-vcpkg

The steps in the root of the beta registry, are about classic mode.
https://github.com/Azure/azure-sdk-vcpkg-betas/#azure-sdk-beta-vcpkg-registry

cc @ronniegeraghty