plugin/k8s_external: added manpage (#2401)
plugin/k8s_external: added manpage (#2401)

Missed this before the release. Add the manpage.

Signed-off-by: Miek Gieben <00b357f94cf3a1145a32703fb42e2d80418ab806@miek.nl>
ii/coredns,miekg/coredns,johnbelamaric/coredns,coredns/coredns,miekg/coredns,yongtang/coredns,chrisohaver/coredns,johnbelamaric/coredns,ii/coredns