Activate bash completion for Windows executable

Signed-off-by: Harald Albers <github@albersweb.de>

contrib/completion/bash/docker

@@ -4423,4 +4423,4 @@ _docker() {
 eval "$__docker_previous_extglob_setting"
 unset __docker_previous_extglob_setting
 
-complete -F _docker docker dockerd
+complete -F _docker docker docker.exe dockerd dockerd.exe