Adding introductory line to D1 pricing FAQs.

Author: Oxyjun

src/content/docs/d1/platform/limits.mdx

@@ -45,6 +45,8 @@ Cloudflare also offers other storage solutions such as [Workers KV](/kv/api/), [
 
 ## Frequently Asked Questions
 
+Frequently asked questions related to D1 limits:
+
 ### How much data can I store in a D1 database?
 
 - With a free plan, each D1 database can store up to 500 MB of data.