A very simple function to draw a progress bar using Unicode.
The Unicode block element symbols allow the graph to have a higher resolution than just one pixel by character. That is each character has has 8 subdivisions.
Horizontally these symbols are used:
▏ ▎ ▍ ▌ ▋ ▊ ▉ █
And vertically these symbols are used:
▁ ▂ ▃ ▄ ▅ ▆ ▇ █
