Change README getting started link to explicit instructions (#66828)
Summary:
This changes the link for installing binaries to the page on pytorch.org that is entirely the download command selector (which isn't visible on a normal aspect ratio screen when the main website page first loads anymore).
This also includes some other random fixes:
* Update HUD link
* Clean ups
Fixes #{issue number}
Pull Request resolved: https://github.com/pytorch/pytorch/pull/66828
Reviewed By: malfet
Differential Revision: D31750654
Pulled By: driazati
fbshipit-source-id: aef9ceba71418f6f7648eab9a8c8a78d6c60518b
