World to Viewport Point & Viewport to World Point operators + Test (#98)

* World to Viewport Point & Viewport to World Point operators + Test

First implementation of World to Viewport Point operator and its reciprocal Viewport to World Point operator.
Includes a test scene for these 2 operators.

* Update CHANGELOG.md

Update Changelog

* Added documentation md files.

Co-authored-by: Lewis Jordan <[email protected]>

Author: 2 people

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