VOXELFORMAT: WOXEL support (xyz)

[mgerhardy]

max region size: 128x128x128

https://github.com/woxels/Woxel/blob/main/main.c

supported export formats by this editor: txt (see below, xyz +rgb), vv, ply

*.wox.gz is the internal format https://github.com/woxels/Woxel/blob/main/inc/excess.h (see game_state struct)

# Woxel.xyz v1.1 / woxels.github.io
# X Y Z RRGGBB
0 -64 64 FFFFFF
1 -64 64 FFFFFF
1 -63 64 FFFFFF
1 -62 64 FFFFFF
2 -62 64 FFFFFF
2 -61 64 FFFFFF
1 -63 65 FFFFFF
1 -62 65 FFFFFF
1 -61 65 FFFFFF
2 -61 65 FFFFFF
2 -60 65 FFFFFF
3 -60 65 FFFFFF
4 -60 65 FFFFFF
4 -59 65 FFFFFF
5 -59 65 FFFFFF
5 -58 65 FFFFFF
6 -58 65 FFFFFF
7 -58 65 FFFFFF
7 -57 65 FFFFFF