Add release note about potential issues with dependencies

Signed-off-by: Leandro Lucarella <[email protected]>

Author: llucax

RELEASE_NOTES.md

@@ -9,3 +9,17 @@ python -m pip install frequenz-sdk
 ```
 
 The GitHub issues were also improved, adding templates for [reporting issues](https://github.com/frequenz-floss/frequenz-sdk-python/issues/new?assignees=&labels=priority%3A%E2%9D%93%2C+type%3Abug&template=bug.yml) and [requesting features](https://github.com/frequenz-floss/frequenz-sdk-python/issues/new?assignees=&labels=part%3A%E2%9D%93%2C+priority%3A%E2%9D%93%2C+type%3Aenhancement&template=feature.yml). Users are also pointed to the [Discussion forums](https://github.com/frequenz-floss/frequenz-sdk-python/issues/new/choose) when trying to open an issue if they have questions instead. Also many labels are assigned automatically on issue and pull request creation.
+
+## Upgrading
+
+Even if there are no breaking changes, you might see this error in your local
+environment when upgrading:
+
+    ERROR: Project file:///home/luca/devel/frequenz-sdk-python has
+    a 'pyproject.toml' and its build backend is missing the 'build_editable'
+    hook. Since it does not have a 'setup.py' nor a 'setup.cfg', it cannot be
+    installed in editable mode. Consider using a build backend that supports PEP
+    660.
+
+If so, you should probably update the dependencies in you virtual environment
+(for example `python -m pip install -U -e .`)