changelog for hard hot reload fix

Author: alexcjohnson

CHANGELOG.md

@@ -10,6 +10,7 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 - [#1237](https://github.com/plotly/dash/pull/1237) Closes [#920](https://github.com/plotly/dash/issues/920): Converts hot reload fetch failures into a server status indicator showing whether the latest fetch succeeded or failed. Callback fetch failures still appear as errors but have a clearer message.
 
 ### Fixed
+- [#1255](https://github.com/plotly/dash/pull/1255) Hard hot reload targets only the current window, not the top - so if your app is in an iframe you will only reload the app
 - [#1249](https://github.com/plotly/dash/pull/1249) Fixes [#919](https://github.com/plotly/dash/issues/919) so `dash.testing` is compatible with more `pytest` plugins, particularly `pytest-flake8` and `pytest-black`.
 - [#1248](https://github.com/plotly/dash/pull/1248) Fixes [#1245](https://github.com/plotly/dash/issues/1245), so you can use prop persistence with components that have dict IDs, ie for pattern-matching callbacks.
 - [#1185](https://github.com/plotly/dash/pull/1185) Sort asset directories, same as we sort files inside those directories. This way if you need your assets loaded in a certain order, you can add prefixes to subdirectory names and enforce that order.