Add a new MAINTAINERS file for the builder.

Docker-DCO-1.1-Signed-off-by: Erik Hollensbe <github@hollensbe.org> (github: erikh)

builder/MAINTAINERS

@@ -0,0 +1,2 @@
+Tibor Vass <teabee89@gmail.com> (@tiborvass)
+Erik Hollensbe <github@hollensbe.org> (@erikh)