Docu update

CITATION

 If you use the Climate Data Operators (CDO) to process data for an article in a scientific publication, please cite:
 
-Schulzweida, Uwe. (2022). CDO User Guide (2.1.0). Zenodo. https://doi.org/10.5281/zenodo.7112925
+Schulzweida, Uwe. (2023). CDO User Guide (2.3.0). Zenodo. https://doi.org/10.5281/zenodo.10020800
 
-@misc{schulzweida_uwe_2022_7112925,
+@misc{schulzweida_2023_10020800,
   author       = {Schulzweida, Uwe},
   title        = {CDO User Guide},
   month        = oct,
-  year         = 2022,
+  year         = 2023,
   publisher    = {Zenodo},
-  version      = {2.1.0},
-  doi          = {10.5281/zenodo.7112925},
-  url          = {https://doi.org/10.5281/zenodo.7112925}
-}
\ No newline at end of file
+  version      = {2.3.0},
+  doi          = {10.5281/zenodo.10020800},
+  url          = {https://doi.org/10.5281/zenodo.10020800}
+}