add VS extension in doc (#63944)
Summary:
add VS extension in https://pytorch.org/cppdocs/installing.html
Pull Request resolved: https://github.com/pytorch/pytorch/pull/63944
Reviewed By: malfet
Differential Revision: D30546156
Pulled By: seemethere
fbshipit-source-id: a65448d8702f9fd400c9dd2ef2d9f961f30c4983
