Add changelog notes

CHANGELOG.md

@@ -2,6 +2,25 @@ Next Version
 ------------
 
 BREAKING CHANGES:
+- If a features store is configured with a layer this layer needs to be an `ol.layer.Vector` with an `ol.source.Vector` 
+with a `ol.Collection`. That means, if you used it like this before, it will now throw an Error:
+```js
+Ext.create('GeoExt.data.store.Features', {
+  layer: new ol.layer.Vector({
+    source: new ol.source.Vector()
+  })
+});
+``` 
+If you change it to the following code it will work and keep the elements of the store, and the layer in sync.
+```js
+Ext.create('GeoExt.data.store.Features', {
+  layer: new ol.layer.Vector({
+    source: new ol.source.Vector({
+      features: new ol.Collection()
+    })
+  })
+});
+``` 
 - The OpenLayers version was updated to v6.5.0. To use this version run `npm i @geoext/openlayers-legacy` and include the
 `ol.js` and `ol.css` files from there.
 - Due to the OpenLayers update the OverviewMap no longer can use the same layers as the main map and always has to be