[x3d-public] LineSet notes

[Andreas Plesch]

Here are couple more LineSet notes:

https://www.web3d.org/documents/specifications/19775-1/V3.3/Part01/components/rendering.html#LineSet

- not clear what happens if there not enough colors in the Color node:
just use last color ?
- not clear if vertexCount field is empty. If there are vertexCounts
they need to 2 and larger. But what if there no vertexCounts. A
reasonable behaviour would be to treat the line as a single line, eg.
vertexCount is a single value, the number of provided points.

Andreas Plesch
Waltham, MA 02453