doc: add star history (#582)

Signed-off-by: Marcin Kubica <marcin@deblock.com>

Author: marcinkubica

README.md

@@ -97,3 +97,13 @@ Thanks to all contributors who are helping to make kagent better.
 <a href="https://github.com/kagent-dev/kagent/graphs/contributors">
   <img src="https://contrib.rocks/image?repo=kagent-dev/kagent" />
 </a>
+
+## Star History
+
+<a href="https://www.star-history.com/#kagent-dev/kagent&Date">
+ <picture>
+   <source media="(prefers-color-scheme: dark)" srcset="https://api.star-history.com/svg?repos=kagent-dev/kagent&type=Date&theme=dark" />
+   <source media="(prefers-color-scheme: light)" srcset="https://api.star-history.com/svg?repos=kagent-dev/kagent&type=Date" />
+   <img alt="Star history of kagent-dev/kagent over time" src="https://api.star-history.com/svg?repos=kagent-dev/kagent&type=Date" />
+ </picture>
+</a>