MAINTAINERS: add me as /proc/kcore maintainer

Christian volunteered me for this a while back given that drgn is the
main user of /proc/kcore and I've touched it several times over the
years.

Link: https://lore.kernel.org/all/20231125-kurhotel-zuwege-10cce62a50fd@brauner/
Signed-off-by: Omar Sandoval <osandov@fb.com>
Link: https://lore.kernel.org/r/fb71665d1d10a8b3faf7930e4ad9d93143a61cef.1731115587.git.osandov@fb.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: osandov

MAINTAINERS

@@ -12385,6 +12385,13 @@ F:	Documentation/kbuild/kconfig*
 F:	scripts/Kconfig.include
 F:	scripts/kconfig/
 
+KCORE
+M:	Omar Sandoval <osandov@osandov.com>
+L:	linux-debuggers@vger.kernel.org
+S:	Maintained
+F:	fs/proc/kcore.c
+F:	include/linux/kcore.h
+
 KCOV
 R:	Dmitry Vyukov <dvyukov@google.com>
 R:	Andrey Konovalov <andreyknvl@gmail.com>