add ATR isotope data addition to changelog

CHANGELOG.md

@@ -5,6 +5,7 @@
 ### New Datasets
 * Add EURECA-MIP boundary conditions deltas (#165). By [torresalavez](https://github.com/torresalavez) and [Hauke Schulz](https://github.com/observingClouds)
 * Add isotope data from BCO (#152). By [Hauke Schulz](https://github.com/observingClouds)
+* Add isotope data from ATR (#158). By [Leonie Villiger](https://github.com/leonie-villiger)
 * Add EUREC4A-MIP boundary conditions from ERA5 and COSMO for current and pseudo-global warming experiment (#135). By [torresalavez](https://github.com/torresalavez) and [Hauke Schulz](https://github.com/observingClouds)
 * Add cloud droplet size distribution from specMACS instrument. By [Veronika Pörtge](https://github.com/vpoertge)
 * Add LICHT lidar data from RV Meteor as provided by the MPI-TCO catalog (#12). By [Leif Denby](https://github.com/leifdenby), [Hauke Schulz](https://github.com/observingClouds), [Tobias Kölling](https://github.com/d70-t) and [Nina Robbins](https://github.com/ninarobbins)