docs: stable-kernel-rules: mention other usages for stable tag comments

docs: stable-kernel-rules: mention other usages for stable tag comments

Document how to delay backporting or send a note to the stable team
using shell-style inline comments attached to stable tags.

CC: Greg KH <gregkh@linuxfoundation.org>
CC: Sasha Levin <sashal@kernel.org>
CC: Jonathan Corbet <corbet@lwn.net>
Signed-off-by: Thorsten Leemhuis <linux@leemhuis.info>
Link: https://lore.kernel.org/r/bf1489b40ff358b7cb4f7d8cc73d5c7c3c143471.1689056247.git.linux@leemhuis.info
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>