Add badge to README that workflow is operational

Author: omad

README.md

@@ -1,3 +1,5 @@
+[![Update Releases](https://github.com/opendatacube/release-tracker/actions/workflows/update.yml/badge.svg)](https://github.com/opendatacube/release-tracker/actions/workflows/update.yml)
+
 # Open Data Cube Release Tracker
 
 This repository tracks the latest releases of Open Data Cube packages from PyPI, GitHub and Conda-forge.
@@ -33,4 +35,4 @@ The `update_releases.py` script fetches the latest version information and gener
 
 You can re-render `index.html` more quickly by running `uv run python update_releases.py`, which uses the local JSON data.
 
-This is useful for updating the template or styles
+This is useful for updating the template or styles