Update RELEASE.md

Author: krassowski

RELEASE.md

@@ -9,7 +9,8 @@ The version for PyPI must be updated in two places:
 - `py_src/jupyter_lsp/_version.py`
 - `azure-pipelines.yml`
 
-The version for npm must be updated in two places:
+The version for npm must be updated in three places:
 
 - `package.json`
 - `azure-pipelines.yml`
+- `README.md`