Add changelog entry

CHANGELOG.md

@@ -18,6 +18,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
+- Fix wrong number of mesh levels when grid is multiple of refinement factor
+  [\#26](https://github.com/mllam/weather-model-graphs/pull/26)
+  @joeloskarsson
+
 - Create different number of mesh nodes in x- and y-direction.
   [\#21](https://github.com/mllam/weather-model-graphs/pull/21)
   @joeloskarsson