changelog for callback graph layout fix

Author: alexcjohnson

CHANGELOG.md

@@ -6,6 +6,9 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 ### Changed
 - [#1376](https://github.com/plotly/dash/pull/1376) Extends the `getTransform` logic in the renderer to handle `persistenceTransforms` for both nested and non-nested persisted props. This was used to to fix [dcc#700](https://github.com/plotly/dash-core-components/issues/700) in conjunction with [dcc#854](https://github.com/plotly/dash-core-components/pull/854) by using persistenceTransforms to strip the time part of the datetime so that datepickers can persist when defined in callbacks.
 
+### Fixed
+- [#1408](https://github.com/plotly/dash/pull/1408) Fixes a bug where the callback graph layout would reset whenever a callback fired, losing user-initiated layout changes ([#1402](https://github.com/plotly/dash/issues/1402)) or creating a new force layout ([#1401](https://github.com/plotly/dash/issues/1401))
+
 ## [1.16.0] - 2020-09-03
 ### Added
 - [#1371](https://github.com/plotly/dash/pull/1371) You can now get [CSP `script-src` hashes](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/script-src) of all added inline scripts by calling `app.csp_hashes()` (both Dash internal inline scripts, and those added with `app.clientside_callback`) .