Update CHANGELOG.md

Author: LiamConnors

Diff for: CHANGELOG.md

@@ -2,6 +2,17 @@
 All notable changes to this project will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
+## UNRELEASED
+
+### Updated
+  - Updated Plotly.js to from version 2.18.2 to version 2.20.0. See the [plotly.js CHANGELOG](https://github.com/plotly/plotly.js/blob/master/CHANGELOG.md#2200----2023-03-15) for more information. Notable changes include:
+    - Add `title.automargin` to enable automatic top and bottom margining for both container and paper referenced titles [[#6428](https://github.com/plotly/plotly.js/pull/6428)],
+   with thanks to [Gamma Technologies](https://www.gtisoft.com/) for sponsoring the related development.
+    - Add `label` attribute to shapes [[#6454](https://github.com/plotly/plotly.js/pull/6454)], with thanks to the [Volkswagen](https://www.volkswagenag.com) Center of Excellence for Battery Systems for sponsoring development!
+    - Add `labelalias` to various axes namely cartesian, gl3d, polar, smith, ternary, carpet,
+   indicator and colorbar [[#6481](https://github.com/plotly/plotly.js/pull/6481)],
+   this feature was anonymously sponsored: thank you to our sponsor!
+
 ## [5.13.1] - 2023-02-24
 
 ### Updated