MAINTAINERS: add page cache reviewer

Add myself as a page cache reviewer since I tend to review changes in
these areas anyway.

[akpm@linux-foundation.org: add linux-mm@kvack.org]
Link: https://lore.kernel.org/20260415174039.13016-2-jack@suse.cz
Signed-off-by: Jan Kara <jack@suse.cz>
Acked-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Acked-by: Lorenzo Stoakes <ljs@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: jankara

MAINTAINERS

@@ -19964,7 +19964,9 @@ F:	kernel/padata.c
 
 PAGE CACHE
 M:	Matthew Wilcox (Oracle) <willy@infradead.org>
+R:	Jan Kara <jack@suse.cz>
 L:	linux-fsdevel@vger.kernel.org
+L:	linux-mm@kvack.org
 S:	Supported
 T:	git git://git.infradead.org/users/willy/pagecache.git
 F:	Documentation/filesystems/locking.rst