Gauge Type: Tank Level: unit configuration

### Description

Can we get configurable unit and presentation for tank level gauge. I like to show value in mm so probably some kind value template will give flexibility to fill wishlist of users. Example something like this: {msg.payload}mm. I am not 100% sure that is it good to do math in node (currenty it convers result to percentage). If it is wanted then template can handle it that way {msg.payload/100}% but I think it is more "standard" way to just let another node do math and let ui node just show raw results and use internal math only for visualisation.

### Have you provided an initial effort estimate for this issue?

I have provided an initial effort estimate