Add upgrade notes after merging wegue-oss#335

This adds some essentials, which have to be done when upgrading a Wegue
application to the lastest master branch, which will become the new v2
soon.

upgrade-notes.md

@@ -2,4 +2,18 @@
 
 ## v1 -> v2
 
-Please fill in breaking changes upgrade steps from v1 to v2
+### OpenLayers
+
+This lists some essentials, which had to be adapted in the Wegue code regarding to the upgrade to OpenLayers in version 7:
+
+- OL `Overlay` no longer accepts `autoPanAnimation` as an option.
+ Now the animation delay is passed as an object directly to the autoPan option.
+- `map.forEachLayerAtPixel()` is removed. Replaced with e.g. `map.getLayers().forEach()`.
+
+Please have a look at the official [OpenLayers upgrade notes](https://github.com/openlayers/openlayers/releases/tag/v7.0.0), when you upgrade your Wegue app.
+
+### Vuetify
+
+This lists some essentials, which had to be adapted in the Wegue code regarding to the upgrade to Vuetify in version 2.6.15:
+
+- The component `<v-content>` was renamed to `<v-main>`. Please adapt this in the `WguAppTemplate.vue` file of your Wegue application.