added traffic light badge to README.md (#125)

# Pull Request

## Description

Added traffic light badge to README.md

## Checklist:

- [ ] My code follows [OCF's coding style
guidelines](https://github.com/openclimatefix/.github/blob/main/coding_style.md)
- [ ] I have performed a self-review of my own code
- [ ] I have made corresponding changes to the documentation
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] I have checked my code and corrected any misspellings

README.md

@@ -1,4 +1,5 @@
 # Photovoltaic (PV) Site Prediction Model
+[![ease of contribution: hard](https://img.shields.io/badge/ease%20of%20contribution:%20hard-bb2629)](https://github.com/openclimatefix/ocf-meta-repo?tab=readme-ov-file#overview-of-ocfs-nowcasting-repositories)
 
 This repo contains code to train and evaluate a model to produce the forecasted energy production from solar panels (PV). It does this by providing a framework to forecast ahead, using pv data from sites, weather data (NWPs as multidimensional geospatial zarrs) and sateliite imagery (from the EUMETSAT Geostationary satellite).