provide GitHub Action to set up vcpkg

[rursprung]

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Is your feature request related to a problem? Please describe.
currently there's no easy/standardised way to use vcpkg in the CI on GitHub using GitHub Actions. you either have to use a 3rd-party action (which may or may not be actively maintained or follow best practices) or do it manually (clone the repo, run the bootstrap, etc.)

Proposed solution
you (the vcpkg team at Microsoft) centrally provide a GitHub Action which can be included which will always set up the latest release of vcpkg and register it in the path, set VCPKG_ROOT, CMAKE_TOOLCHAIN_FILE, etc.

the action could then also taking care of doing a shallow clone of the repo, caching it, etc. to reduce the load on GitHub if it's used often, if this is required.

Describe alternatives you've considered
instead of providing this as an action it could also be backed directly into the base images used by the GitHub Actions - after all, GitHub belongs to Microsoft :)
other build tools (e.g. rust) are also always installed by default, though maybe the user base of vcpkg isn't large enough yet to support this? and vcpkg might be updated more often than the base image, so having an action installing it might be better

Additional context

• search for current vcpkg related actions