Add release notes

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

Author: llucax

RELEASE_NOTES.md

@@ -30,7 +30,10 @@ But you might still need to adapt your code:
 
 ## Bug Fixes
 
-<!-- Here goes notable bug fixes that are worth a special mention or explanation -->
+- `setuptools.grpc_tools`: Fix wrong passing of include paths when passed via:
+
+    * Command-line: Now extra white-spaces and empty strings are removed, before they were passed to `protoc -I`.
+    * `pyproject.toml`: Now an empty array/list can be passed to override the default paths, before this resulted in an empty string being passed to `protoc -I`.
 
 ### Cookiecutter template