contrib/gitdm: un-ironically add a mapping for LWN

I think this mainly comes from kernel-doc stuff imported into the QEMU
tree.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Cc: Jonathan Corbet <corbet@lwn.net>
Message-Id: <20210720232703.10650-14-alex.bennee@linaro.org>