doc/go1.12: document RSA-PSS support in crypto/tls
doc/go1.12: document RSA-PSS support in crypto/tls

Change-Id: I9350e5a72e3c375f6b76897708f09f1f50c7be14
Reviewed-on: https://go-review.googlesource.com/c/155482
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/go,CAFxX/go,nawawi/go,josharian/go,CAFxX/go,josharian/go,josharian/go,cloudflare/go,akutz/go,cloudflare/go,josharian/go,CAFxX/go,akutz/go,golang/go,josharian/go,golang/go,cloudflare/go,nawawi/go,golang/go,nawawi/go,akutz/go,nawawi/go,cloudflare/go,josharian/go,josharian/go,CAFxX/go,akutz/go,akutz/go,cloudflare/go,CAFxX/go,akutz/go,cloudflare/go,CAFxX/go,CAFxX/go,josharian/go,golang/go,nawawi/go,golang/go,cloudflare/go,nawawi/go,CAFxX/go,akutz/go,akutz/go,golang/go,cloudflare/go,nawawi/go,golang/go,nawawi/go