Add Fred as docs MAINTAINER

Docker-DCO-1.1-Signed-off-by: SvenDowideit <SvenDowideit@home.org.au> (github: SvenDowideit)

docs/MAINTAINERS

@@ -1,3 +1,4 @@
 James Turnbull <james@lovedthanlost.net> (@jamtur01)
 Sven Dowideit <SvenDowideit@fosiki.com> (@SvenDowideit)
 O.S. Tezer <ostezer@gmail.com> (@OSTezer)
+Fred Lifton <fred.lifton@docker.com> (@fredlf)