[steam-audio] Adding port

[Honeybunch]

Adding this port for those of us who crave spatial audio

• [X] Changes comply with the maintainer guide.
• [X] 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.
• [X] The versioning scheme in vcpkg.json matches what upstream says.
• [X] The license declaration in vcpkg.json matches what upstream says.
• [X] The installed as the "copyright" file matches what upstream says.
• [X] The source code of the component installed comes from an authoritative source.
• [X] The generated "usage text" is accurate. See adding-usage for context.
• [X] The version database is fixed by rerunning ./vcpkg x-add-version --all and committing the result.
• [X] Only one version is in the new port's versions file.
• [X] Only one version is added to each modified port's versions file.