feat: expose point order

[flekschas]

This PR introduces pointOrder to allow changing the draw order without having to re-upload data

Description

What was changed in this pull request?

Added a pointOrder property (null | number[]) that controls point draw order by reordering entries in normalPointsIndexBuffer. When set, the array specifies the sequence in which points are rendered (first = behind, last = on top), with missing indices appended sequentially; the ordering is preserved through filter()/unfilter() and resets automatically when draw() is called with different-length data.

Example

Why is this PR necessary?

Fixes #162

Checklist

• Provided a concise title as a semantic commit message (e.g. "fix: correctly handle undefined properties")
• CHANGELOG.md updated
• Tests added or updated
• Documentation in README.md added or updated
• Example(s) added or updated
• Screenshot, gif, or video attached for visual changes