Update to include "octant" Unicode 16.0 characters as a drawing possibility

[jsbueno]

Unicode 16.0 had added \U0001cd00 - \U0001cde5 "Octant" chars allowing 8 subpixels per char block.

ref:

https://www.unicode.org/charts/PDF/Unicode-16.0/U160-1CC00.pdf

Terminedia already supports 1 block, 1/2 block, 1/4 block and 1/8 block with Braille (which is not intended for subpixel drawing) - - adding octants is a natural feature, and I should do it as soon as possible.

Python 3.14 should come with Unicode 16 support - but that is only needed for getting the chars by name - otherwise all one needs is a compatible font installed.