docs: link methodology/editorial-policy/demo pages, credit author

Reinforces the entity signal between this repo and costkits.com/about/
(John Caruso, FSA, MAAA) and adds the interactive demo + methodology
page links that were missing.

Author: jc

README.md

@@ -89,7 +89,11 @@ Estimates are built from CMS hospital price transparency files, Medicare fee sch
 
 ## Links
 
-[costkits.com](https://costkits.com) · [API docs](https://costkits.com/api/) · [Get an API key](https://costkits.com/api-keys) · [MCP server](https://github.com/costkits/costkits-mcp)
+[costkits.com](https://costkits.com) · [API docs](https://costkits.com/api/) · [Interactive demo](https://costkits.com/api/demo/) · [Get an API key](https://costkits.com/api-keys) · [MCP server](https://github.com/costkits/costkits-mcp)
+
+## About CostKits
+
+CostKits is a healthcare cost-transparency platform built and maintained by [John Caruso, FSA, MAAA](https://costkits.com/about/) — a healthcare actuary with 20+ years in insurance pricing, medical billing systems, and healthcare cost analytics. This API is the same pricing engine behind [costkits.com](https://costkits.com)'s consumer tools (cost estimator, provider price comparison, bill analyzer). See our [data & pricing methodology](https://costkits.com/methodology/) for exactly how estimates are sourced, and our [editorial policy](https://costkits.com/editorial-policy/) for how we handle accuracy and corrections.
 
 ## Support