Document the add/remove/substitute changes in #982

Author: jasongrout

CHANGELOG.md

@@ -18,6 +18,14 @@ Here are some highlights of changes in this version. See the full list of change
   * `legend.positionnning` -> `legend.position`
 
   The recommended way to create a LegendControl with a given title is to use the `title` parameter: `LegendControl({}, title='My Title')`. There is a backwards compatibility shim in place, so giving the title as `name` in the constructor still works, but is not recommended: `LegendControl({}, name='My Title')`
+* Deprecate layer and control-specific methods for maps, in favor of methods that work for both layers and controls [#982](https://github.com/jupyter-widgets/ipyleaflet/pull/982). Update your code with the following substitutions for a Map `map`:
+  * `map.add_control(...)` or `map.add_layer(...)` -> `map.add(...)`
+  * `map.remove_control(...)` or `map.remove_layer(...)` -> `map.remove(...)`
+  * `map.remove_control(...)` or `map.remove_layer(...)` -> `map.remove(...)`
+  * `map.substitute_control(...)` or `map.substitute_layer(...)` -> `map.substitute(...)`
+  * `map.clear_controls(...)` or `map.clear_layers(...)` -> `map.clear(...)`
+
+  The inline operators still continue to work as before, such as `map += control` or `map -= layer`.
 
 ### Maintenance