JSFiddle - React, Tailwind, and code Playground

HTML

<textarea id="demo-textarea">
TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT TEXT </textarea>

CSS

#demo-textarea
{
  width:100%;
  height:395px;
}

textarea
{
  line-height: 4ch;
  background-image: linear-gradient(transparent, transparent calc(4ch - 1px), #E7EFF8 0px);
  background-size: 100% 4ch;
}