feat: enable Mailchimp

Author: danieldanielecki

data/siteMetadata.js

@@ -52,7 +52,7 @@ const siteMetadata = {
   newsletter: {
     // supports mailchimp, buttondown, convertkit, klaviyo, revue, emailoctopus, beehive
     // Please add your .env file and modify it according to your selection
-    provider: 'buttondown',
+    provider: 'mailchimp',
   },
   comments: {
     // If you want to use an analytics provider you have to add it to the