doc/go1.13: mention {NetBSD,OpenBSD}/arm64 ports
doc/go1.13: mention {NetBSD,OpenBSD}/arm64 ports

Also alphabetize port listing.

Change-Id: I4cc552a74856c9955571d721deb6223438c7d856
Reviewed-on: https://go-review.googlesource.com/c/go/+/183637
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>

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