Character Counter | PCF Gallery - released new control for it. hope this helps

please check out the below 

PCF.Study/Charecter Counter at master · astav2/PCF.Study (github.com)

I would love to give it a try for textbox type fields

A plugin would be able to cater this request. but what is the need of a control or can you please elaborate more on your idea like what kind of control you are looking for visually. 

is someone developing this or already done? would like to take this up