[cpp-async] Add new port

[chausner]

This adds the cpp-async library as a new port.

• Changes comply with the maintainer guide
• The name of the port matches an existing name for this component on https://repology.org/ if possible, and/or is strongly associated with that component on search engines.
• x] Optional dependencies are resolved in exactly one way. For example, if the component is built with CMake, all find_package calls are REQUIRED, are satisfied by vcpkg.json's declared dependencies, or disabled with CMAKE_DISABLE_FIND_PACKAGE_Xxx
• The versioning scheme in vcpkg.json matches what upstream says.
• The license declaration in vcpkg.json matches what upstream says.
• The installed as the "copyright" file matches what upstream says.
• The source code of the component installed comes from an authoritative source.
• The generated "usage text" is accurate. See adding-usage for context.
• The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• Only one version is in the new port's versions file.
• Only one version is added to each modified port's versions file.

[chausner]

The upstream repository uses a vcpkg manifest (https://github.com/microsoft/cpp-async/blob/main/vcpkg.json) but I think the manifests in this repository are independent, right?

[chausner]

@davidmatson Are official versioned releases planned for cpp-async? If yes, would you suggest that we wait for the first release before publishing a vcpkg port? This PR is using date-based versioning at the moment since there is no official release yet.

[davidmatson]

@davidmatson Are official versioned releases planned for cpp-async? If yes, would you suggest that we wait for the first release before publishing a vcpkg port? This PR is using date-based versioning at the moment since there is no official release yet.

Good question. I was planning on publishing a separate release zip, but I could tag the current branch as v1.0.0. Thoughts?

And thanks for doing this port!

[chausner]

Good question. I was planning on publishing a separate release zip, but I could tag the current branch as v1.0.0. Thoughts?

If there are official releases, a release tag would make a lot of sense, yes.

And thanks for doing this port!

Thank you for publishing the library. ;)

[davidmatson]

If there are official releases, a release tag would make a lot of sense, yes.

Done - it's v1.0.0 now.