changelog for clientside callback_context

Author: carl-dawson

CHANGELOG.md

@@ -2,8 +2,9 @@
 All notable changes to `dash` will be documented in this file.
 This project adheres to [Semantic Versioning](http://semver.org/).
 
-## [1.12.0] - 2020-05-05
+## [UNRELEASED]
 ### Added
+- [#1240](https://github.com/plotly/dash/pull/1240) Adds `callback_context` to clientside callbacks (e.g. `dash_clientside.callback_context.triggered`). Supports `triggered`, `inputs`, `inputs_list`, `states`, and `states_list`, all of which closely resemble their serverside cousins.
 - [#1228](https://github.com/plotly/dash/pull/1228) Adds control over firing callbacks on page (or layout chunk) load. Individual callbacks can have their initial calls disabled in their definition `@app.callback(..., prevent_initial_call=True)` and similar for `app.clientside_callback`. The app-wide default can also be changed with `app=Dash(prevent_initial_callbacks=True)`, then individual callbacks may disable this behavior.
 - [#1201](https://github.com/plotly/dash/pull/1201) New attribute `app.validation_layout` allows you to create a multi-page app without `suppress_callback_exceptions=True` or layout function tricks. Set this to a component layout containing the superset of all IDs on all pages in your app.
 - [#1078](https://github.com/plotly/dash/pull/1078) Permit usage of arbitrary file extensions for assets within component libraries