refactor: extract duplicated velocity calculation logic in Contact class

[diogomene]

What was done?

To eliminate the code duplication identified in the Contact class during the calculation of the relative velocity between two contact points (bodies A and B), the repeated instructions were extracted and centralized into a method named computeRelativeVelocity within the Contact class:

computeRelativeVelocity(
  dv: Vec2Value,
  vA: Vec2Value,
  wA: number,
  rA: Vec2Value,
  vB: Vec2Value,
  wB: number,
  rB: Vec2Value
): void {
  matrix.zeroVec2(dv);
  matrix.plusVec2(dv, vB);
  matrix.plusVec2(dv, matrix.crossNumVec2(temp, wB, rB));
  matrix.minusVec2(dv, vA);
  matrix.minusVec2(dv, matrix.crossNumVec2(temp, wA, rA));
}

This function takes the required parameters and performs the necessary calculations in-place by reference.

With this solution, the duplication has been effectively addressed, improving both the readability and understanding of the code through modularization and reuse of instructions. Additionally, any future changes to the calculation logic can now be made in a single function, avoiding the need to update all three occurrences of the routine.

Resolves #305

[shakiba]

@diogomene thanks reviewing the code and finding potential improvements. The code is intentionally verbos to make it easier to read, debug, and profile for performance optimization. It's also easier for browser to optimize at runtime.

As you mentioned, verbos and repetitive code is more difficult when you update the logic, however we almost don't change the logic.