docs(example): DraggableBox does not follow the cursor smoothly

[ksokolovskyi]

Description

This PR makes the DraggableBox movement more smooth and predictable by: 1) adjusting FixtureDef and MouseJointDef parameters 2) setting the MouseJoint target to game.screenToWorld(event.deviceEndPosition) rather than event.localEndPosition

Fixes https://github.com/flame-engine/flame/issues/3203

The comparison recordings are presented below:

GearJointExample

| BEFORE | AFTER | |----------|----------| |

PrismaticJointExample

| BEFORE | AFTER | |----------|----------| |

PulleyJointExample

| BEFORE | AFTER | |----------|----------| |

RopeJointExample

| BEFORE | AFTER | |----------|----------| |

Checklist

• [X] I have followed the Contributor Guide when preparing my PR.
• [ ] I have updated/added tests for ALL new/updated/fixed functionality.
• [ ] I have updated/added relevant documentation in docs and added dartdoc comments with ///.
• [X] I have updated/added relevant examples in examples or docs.

Breaking Change?

• [ ] Yes, this PR is a breaking change.
• [X] No, this PR is not a breaking change.

Related Issues

[ksokolovskyi]

@spydon thanks for the review and merge!