feat(syndicator-mastodon): validate url setup prompt

Author: paulrobertlloyd

packages/syndicator-mastodon/index.js

@@ -74,7 +74,10 @@ export default class MastodonSyndicator {
         type: "text",
         name: "url",
         message: "What is the URL of your Mastodon server?",
-        description: "i.e. https://mastodon.social",
+        validate: (value) =>
+          URL.canParse(value)
+            ? true
+            : "Enter a valid URL, for example https://mastodon.social",
       },
       {
         type: "text",