docs: update release notes step to use --notes-file

Author: euxx

RELEASE.md

@@ -55,12 +55,23 @@
 
 <!-- END-SHARED -->
 
-7. Update the release notes on GitHub to match CHANGELOG.md:
+7. Update the release notes on GitHub to match `CHANGELOG.md`:
+
+   Write the notes in Markdown format to a temp file, then pass it via `--notes-file`:
 
    ```sh
-   gh release edit vX.Y.Z --notes "## Improved
+   gh release edit vX.Y.Z --notes-file /path/to/notes.md
+   ```
+
+   Notes format:
+
+   ```markdown
+   ## What's Changed
+
+   ### Added/Changed/Fixed
+
    - Change 1
    - Change 2
 
-   **Full Changelog**: https://github.com/euxx/github-notifier-pro/compare/vPREV...vX.Y.Z"
+   **Full Changelog**: https://github.com/euxx/github-notifier-pro/compare/vPREV...vX.Y.Z
    ```