Change Note Block Sprites

[ShinkoNet]

There is an option to change it from using colors to displaying the note block instrument already, but it is ugly.

A lot of the new sounds use similar colours to other instruments (like Bit looking similar to Double Bass, and Xylophone looking similar to Harp), and this inconveniences people who are color blind or under poor light conditions.

What could be done would be altering the shapes of the note blocks, to help differentiate each instrument further. Double bass could be a circular sprite, and xylophone could be a diamond shape. Didgeridoo could be a half-slab.

Example image:

[ShinkoNet]

Added to dark mode in #36