feat(docker): add image prune alias (#12520)

Co-authored-by: Carlo Sala <carlosalag@protonmail.com>

plugins/docker/docker.plugin.zsh

@@ -6,6 +6,7 @@ alias dib='docker image build'
 alias dii='docker image inspect'
 alias dils='docker image ls'
 alias dipu='docker image push'
+alias dipru='docker image prune -a'
 alias dirm='docker image rm'
 alias dit='docker image tag'
 alias dlo='docker container logs'