Add initial prototype.

3-mid/physics/implement/box2d/contrib/CHANGELOG.md

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+# Changes for version 2.4.1
+
+## API Changes
+- Extended distance joint to have a minimum and maximum limit.
+- Removed rope joint. Use the distance joint instead.
+- B2_USER_SETTINGS and b2_user_settings.h can control user data, length units, and maximum polygon vertices.
+- Default user data is now uintptr_t instead of void*
+- b2FixtureDef::restitutionThreshold lets you set the restitution velocity threshold per fixture.
+
+## BREAKING Changes
+- BREAKING: distance joint 0 stiffness now means the spring is turned off rather than making the joint rigid.
+- BREAKING: distance joint minimum and maximum must be set correctly to get old behavior.
+
+## Infrastructure
+- Library installation function available in CMake.
+- Shared library (DLL) option available.
+- Bug fixes
+
+# Changes for version 2.4.0
+
+## Infrastructure
+- Documentation in Doxygen format
+- CMake build system
+- Unit test support
+- Continuous integration testing using Travis CI
+- Limited use of C++11 (nullptr and override)
+- Restructured folders and renamed files to better match open-source standards
+- MIT License
+- Removed float32 and float64
+- Linked the Box2D project to GitHub Sponsors
+
+## Collision
+- Chain and edge shape must now be one-sided to eliminate ghost collisions
+- Broad-phase optimizations
+- Added b2ShapeCast for linear shape casting
+
+## Dynamics
+- Joint limits are now predictive and not stateful
+- Experimental 2D cloth (rope)
+- b2Body::SetActive -> b2Body::SetEnabled
+- Better support for running multiple worlds
+- Handle zero density better
+  - The body behaves like a static body
+  - The body is drawn with a red color
+- Added translation limit to wheel joint
+- World dump now writes to box2d_dump.inl
+- Static bodies are never awake
+- All joints with spring-dampers now use stiffness and damping
+- Added utility functions to convert frequency and damping ratio to stiffness and damping
+
+## Testbed
+- Testbed uses dear imgui
+- glad OpenGL loader
+- OpenGL 3.3 required
+
+# Changes for version 2.3.0
+- Polygon creation now computes the convex hull. Vertices no longer need to be ordered.
+- The convex hull code will merge vertices closer than dm_linearSlop. This may lead to failure on very small polygons.
+- Added b2MotorJoint.
+- Bug fixes.