Feature request: Finer precision using box-drawing characters

[cooperuser]

It would be awesome if the precision of the top and bottom of the scrollbar can show different percentages of a filled cell instead of being either filled character or nothing. This can be done using characters such as ▁ ▂ ▃ ▄ ▅ ▆ ▇ █ 🮆 🮅 🮄 ▀ 🮃 🮂 ▔

If I find the time I would be interested in implementing this myself, but I am pretty busy currently so I decided to make an issue for it first.

Thanks! And great plugin!