MAINTAINERS: add mailing list for man-pages

Nowadays, man-pages has an associated mailing list.  Mention that list
in MAINTAINERS.

Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

MAINTAINERS

@@ -2704,6 +2704,7 @@ MAN-PAGES: MANUAL PAGES FOR LINUX -- Sections 2, 3, 4, 5, and 7
 P:	Michael Kerrisk
 M:	mtk.manpages@gmail.com
 W:	http://www.kernel.org/doc/man-pages
+L:	linux-man@vger.kernel.org
 S:	Supported
 
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