Label the showScale bar on Treemap

[Tanmay Gupta]

I'm plotting data as a tree map, with the option of showScale='true' color gradient scale from minColor to maxColor along the top of the chart. But I would also like to label the gradient scale as low on one end and high on other end or with a minimum/maximum value. Please help me with the possible options. Let me know if more details are required. Thanks much.