Updated 100-spline.md: Added a video about splines (#5930)

* Added a video about splines

Co-authored-by: dsh <daniel.s.holdsworth@gmail.com>

src/data/roadmaps/game-developer/content/101-game-mathematics/106-orientation/100-spline.md

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 # Spline
 
 `Spline` is a mathematical function widely used in computer graphics for generating curves and surfaces. It connects two or more points through a smooth curve, often used in games for defining pathways, movement paths, object shapes, and flow control. Splines are not confined to two dimensions and can be extended to 3D or higher dimensions. Types of splines include `Linear`, `Cubic`, and `Bezier` splines. While linear splines generate straight lines between points, cubic and bezier splines provide more control and complexity with the addition of control points and handles. Developing a good understanding of splines and their usage can vastly improve the fluidity and visual aesthetics of a game.
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+Learn more from the following resources:
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+- [@Video@ In-depth video about Splines by Freya Holmér](https://youtu.be/jvPPXbo87ds?si=JX_G-gS81tOwQwjf)