This function will create a ComplexHeatmap::columnAnnotation object with rows
for each variable passed as argument. Character columns will be coerced into factors.
For factors, the ColorBrewer palette Set3 will be used. For non-negative numeric, the
PuBu palette will be used, and for columns with negative values, the reversed RdBu will be used.
create_annotations(df, selected_variables)a data frame. It can be an original unscaled data, or a scaled one
list of columns in the data frame to create annotations for
a ComplexHeatmap::columnAnnotation object