docs: fix header

Author: boneskull

site/src/content/docs/index.mdx

@@ -100,7 +100,7 @@ We built **modestbench** because we got tired of:
 - **Tracking results manually** - Automatic history with comparison tools so you can prove your optimizations worked
 - **Writing our own reporters** - Multiple options—optionally running simultaneously—because we can
 
-### What You Get
+## What You Get
 
 - ~~One~~ **Two engines** - Fast `tinybench` for development, `accurate` for when you need the receipts
 - **Advanced statistics** - IQR outlier removal, coefficient of variation, percentiles (statistics nerd stuff)