improve primitives node

[mreinstein]

• There's an arbitrary size restriction on the number of primitives allowed. This is dumb. Maybe growable arrays would be a nice way to allow it grow as needed.
• There should be some kind of viewport culling. It's dumb rendering a bunch of triangles that are outside the viewport.

[mreinstein]

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/ArrayBuffer/resizable

[mreinstein]

for the viewport culling I'll start with something naive. Maybe just an aabb/overlap check with the viewport.