feat: restructure docs into store, marketing, builder, and config sections

contents/docs/marketing/newsletter.md

@@ -0,0 +1,20 @@
+---
+title: Newsletter
+description: Manage subscribers and campaigns.
+---
+
+# Newsletter
+
+A complete email marketing solution built into your store.
+
+## Subscribers
+Automatically capture emails at checkout or via the footer form.
+*   **GDPR**: Includes double opt-in support.
+*   **Segmentation**: Tag subscribers based on purchase history.
+
+## Campaigns
+Send beautiful HTML emails to your list.
+1.  Go to **Marketing > Newsletter**.
+2.  Click **New Campaign**.
+3.  Use the Template Builder to design your email.
+4.  Schedule or send immediately.