MAINTAINERS: direct process doc changes to a dedicated ML

It's hard to keep track of changes to the process docs.
Subsystem maintainers should probably know what's going on,
to ensure reasonably uniform developer experience across
trees.

We also need a place where process discussions can be held
(i.e. designated mailing list which can be CCed on naturally
arising discussions). I'm using workflows@ in this RFC,
but a new list may be better.

No change to the patch flow intended.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20230511020204.910178-1-kuba@kernel.org