MAINTAINERS: Extend the device fuzzing section

The file docs/devel/fuzzing.txt should be in this section, too, and add
myself as a reviewer (since I often take the fuzzer patches through the
qtest-next tree, I should be notified on patches, too).

Message-Id: <20200721053926.17197-1-thuth@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

MAINTAINERS

@@ -2449,9 +2449,11 @@ M: Alexander Bulekov <alxndr@bu.edu>
 R: Paolo Bonzini <pbonzini@redhat.com>
 R: Bandan Das <bsd@redhat.com>
 R: Stefan Hajnoczi <stefanha@redhat.com>
+R: Thomas Huth <thuth@redhat.com>
 S: Maintained
 F: tests/qtest/fuzz/
 F: scripts/oss-fuzz/
+F: docs/devel/fuzzing.txt
 
 Register API
 M: Alistair Francis <alistair@alistair23.me>