Mention that an automated workflow exists for updating the node version

Author: robertbrignull

docs/node-version.md

@@ -1,5 +1,8 @@
 # Node version
 
+> [!NOTE]
+> It should not be necessary to update the Node.js version manually. The [update-node-version.yml](https://github.com/github/vscode-codeql/blob/main/.github/workflows/update-node-version.yml) workflow runs daily and will open a pull request if the Node.js version needs to be updated.
+
 The CodeQL for VS Code extension defines the version of Node.js that it is intended to run with. This Node.js version is used when running most CI and unit tests.
 
 When running in production (i.e. as an extension for a VS Code application) it will use the Node.js version provided by VS Code. This can mean a different Node.js version is used by different users with different versions of VS Code.