[cxxgraph] Add new port CXXGraph

[QuantumFelidae]

• 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.
• 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.

[QuantumFelidae]

@microsoft-github-policy-service agree

[FrankXie05]

Note: I will be converting your PR to draft status. When you respond, please revert to "ready for review".
That way, I can be aware that you've responded since you can't modify the tags.

[FrankXie05]

The usage tested successfully on x64-windows.

[QuantumFelidae]

The PR was not marked as draft, so consider this comment to be marking as ready for review :)

[BillyONeal]

Looks great, thanks for the new port!