add rudimentary fish completions for docker network
add rudimentary fish completions for docker network

Signed-off-by: Tim Sampson <5ee0edb9e2229c0838f1959779f1949031de0123@sampson.fi>

cpuguy83/cli,docker/cli,docker/cli,cpuguy83/cli,thaJeztah/cli,thaJeztah/cli