[examples] Add examples shapes_math_sine_cosine (#5209)

[oqu]

TL;DR #5209 is asking for more examples. This PR is for the example shapes_math_sine_cosine

Summary

Added a new example shapes_math_sine_cosine.c that demonstrates the relationship
between the unit circle and the sine / cosine functions. The example is a C port
of the p5.js "angles and motion: sine/cosine" demo and uses raylib for rendering
and raygui for a small control panel.

Key features:

• Interactive animation of a point moving around a circle (uniform circular motion).
• Sine (red) and Cosine (orange) graphs plotted below the circle.
• Vertical tracker line and moving graph points synchronized with the circular motion.
• Play / Pause control implemented with a raygui toggle.
• Control panel positioned on the right side of the window.

Changelog

• examples/shapes/shapes_math_sine_cosine.c — NEW: main example source
• examples/shapes/shapes_math_sine_cosine.png — optional screenshot.

Possible areas of improvement

• Make the circle and line thicker
• Use constant for the menu layout

Tests

Manually tested on macos by building raylib, then building the example.

cd raylib/src
make -s

cd ../examples
make -s shapes/shapes_math_sine_cosine

Let me know if you need any changes