Changelog: Add entry for website docs of dockerized webnode

Author: iostat

CHANGELOG.md

@@ -13,6 +13,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
   ([#1736](https://github.com/o1-labs/mina-rust/pull/1736))
 - **Web Node**: fix webnode build, add quality-of-life improvements when running
   webnode in Docker. ([#1778](https://github.com/o1-labs/mina-rust/pull/1778))
+- **Web site**: Document running the webnode in Docker ([#1778](https://github.com/o1-labs/mina-rust/pull/1778))
 
 ### Changes