feat: add --machine to secret ls

See coop-cloud/organising#481

cli/app/secret.go

@@ -356,6 +356,7 @@ var appSecretLsCommand = cli.Command{
 		internal.DebugFlag,
 		internal.OfflineFlag,
 		internal.ChaosFlag,
+		internal.MachineReadableFlag,
 	},
 	Before:       internal.SubCommandBefore,
 	Usage:        "List all secrets",
@@ -407,7 +408,11 @@ var appSecretLsCommand = cli.Command{
 		}
 
 		if table.NumLines() > 0 {
-			table.Render()
+			if internal.MachineReadable {
+				table.JSONRender()
+			} else {
+				table.Render()
+			}
 		} else {
 			logrus.Warnf("no secrets stored for %s", app.Name)
 		}