Updated metadata bug in annual_average

- Dim and coord metadata was not preserved for DataArray
  objects when performing an annual average

src/momlevel/util.py

@@ -88,6 +88,12 @@ def _find_ann_midpoint(year, calendar=calendar):
         for var in list(result.variables):
             result[var].attrs = xobj[var].attrs if var in list(xobj.variables) else {}
 
+    for coord in list(result.coords):
+        result[coord].attrs = xobj[coord].attrs if coord in list(xobj.coords) else {}
+
+    for dim in list(result.dims):
+        result[dim].attrs = xobj[dim].attrs if dim in list(xobj.dims) else {}
+
     result.attrs = xobj.attrs
 
     return result