Add bash completion for `--project-directory`

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

contrib/completion/bash/docker-compose

@@ -160,6 +160,10 @@ _docker_compose_docker_compose() {
 			_filedir "y?(a)ml"
 			return
 			;;
+		--project-directory)
+			_filedir -d
+			return
+			;;
 		$(__docker_compose_to_extglob "$daemon_options_with_args") )
 			return
 			;;
@@ -554,6 +558,7 @@ _docker_compose() {
 	local daemon_options_with_args="
 		--file -f
 		--host -H
+		--project-directory
 		--project-name -p
 		--tlscacert
 		--tlscert