[steam-audio] Adding port

[Honeybunch]

Adding this port for those of us who crave spatial audio

• 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.

[Honeybunch]

Friendly bump that this is ready for review 😃

[dg0yt]

Shouldn't this be used by find_dependency calls?

[Honeybunch]

A bit of monkey see monkey do here from me. I was following the pattern that other packages like EASTL, bullet3 and others were doing. This is used as part of a .cmake.in file that's used to generate the dependency import routine IIRC. A bit of a weak spot here in my cmake knowledge though.

[JavierMatosD]

@Honeybunch, please mark "ready for review" once you have responded to @FrankXie05 / @dg0yt review comments. Thanks!

[Honeybunch]

I am trying to upstream what parts of this patch I can but the Steam-Audio repo hasn't seen activity for two months so it may take a while