Unicode Progress Bar

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:
`▁` `▂` `▃` `▄` `▅` `▆` `▇` `█`

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