* [libvpx] Add cmake config file
This allows libvpx to be used with
find_package(libvpx CONFIG REQUIRED)
target_link_libraries(main PRIVATE libvpx::libvpx)
Tested on all supported windows triplets.
* [libvpx] Rename cmake config file to make clear it is unofficial
* [libvpx] Add cmake config target guard
* [libvpx] Update version
