Add list-domains command

Setup.hs

@@ -1,2 +0,0 @@
-import Distribution.Simple
-main = defaultMain

app/Main.hs

@@ -20,7 +20,7 @@ opts = info
 -- | App CLI commands
 commands :: Parser (IO ())
 commands = hsubparser
-  (command "watch"
+  (  command "watch"
        (info
          (   watch . S.fromList <$> some
                (Domain <$> strArgument
@@ -35,6 +35,11 @@ commands = hsubparser
                <> help  "Watch all domains including NSGlobalDomain"
                )
          )
-      (progDesc "Watch domain(s) for changes")
+         $ progDesc "Watch domain(s) for changes"
+       )
+  <> command "list-domains"
+       (info
+         (pure $ S.toList <$> domains >>= mapM_ (putStrLn . coerce))
+         (progDesc "List all domains")
        )
   )