Merge pull request #65 from ESMValGroup/add_cmug4

Add CMUG Phase 4 to acknowledgements

acknowledgements.md

@@ -16,6 +16,7 @@ The development of the ESMValTool was/is funded by
 | ![CRESCENDO](/assets/img/CRESCENDO_logo_square.png) | the European Commission's Horizon 2020 Framework Programme, under Grant Agreement number 641816, the "Coordinated Research in Earth Systems and Climate: Experiments, kNowledge, Dissemination and Outreach ([CRESCENDO](https://ukesm.ac.uk/crescendo/))" | 11/2015-03/2021 |
 | ![CMUG](/assets/img/cmug.jpg) | the European Space Agency's Climate Change Initiative Climate Modelling User Group ([CMUG](https://climate.esa.int/en/projects/cmug/)) Phase 2 | 07/2014-06/2017 |
 | ![CMUG](/assets/img/cmug.jpg) | the European Space Agency's Climate Change Initiative Climate Modelling User Group ([CMUG](https://climate.esa.int/en/projects/cmug/)) Phase 3 | 10/2018-09/2022 |
+| ![CMUG](/assets/img/cmug.jpg) | the European Space Agency's Climate Change Initiative Climate Modelling User Group ([CMUG](https://climate.esa.int/en/projects/cmug/)) Phase 4 | 10/2023-09/2026 |
 | ![EMBRACE](/assets/img/embrace_square.jpg) | the European Commission's 7th Framework Programme, under Grant Agreement number 282672, the "Earth system Model Bias Reduction and assessing Abrupt Climate change ([EMBRACE](https://cordis.europa.eu/project/id/282672/))" project | 11/2011-02/2016 |
 | ![ESM2025](/assets/img/esm2025.jpg) | the European Commission's 7th Framework Programme, under Grant Agreement number 101003536, the "Earth system models for the future ([ESM2025](https://cordis.europa.eu/project/id/101003536/))" project | 06/2021-05/2025 |
 | ![eWaterCycle](/assets/img/eWaterCycle_logo_square.png) | the NWO ([eWaterCycle II](https://www.ewatercycle.org/))" project | - |