add public demo link to docs

Author: msukkari

docs/docs/overview.mdx

@@ -4,6 +4,8 @@ title: "Overview"
 
 > Sourcebot is an open-source ([GitHub](https://github.com/sourcebot-dev/sourcebot)), self-hosted code search tool that is purpose built to help teams find and navigate code quickly, at scale.
 
+If you'd like to try it out, check out our [public demo](https://demo.sourcebot.dev/).
+
 <AccordionGroup>
   <Accordion title="Why Sourcebot?">
     - **Full-featured search:** Fast indexed-based search with regex support, filters, branch search, boolean logic, and more.