[FEATURE] Increase spring stiffness and velocity limits for realistic physics (#1039)

[lixiaolin94]

Summary

This PR implements the feature request from issue #1039 to increase the
maximum limits for spring animation stiffness and velocity parameters,
enabling more realistic physics-based animations.

Changes

• Stiffness limit: Increased from 1,000 to 10,000 (10x increase)
• Velocity limit: Increased from ±1,000 to ±10,000 (10x increase)
• Updated both constructor and setter methods to use new limits
• Added comprehensive test coverage for the new limits
• Fixed rollup configuration import syntax for better Node.js
  compatibility

Example Usage

// Now possible with increased limits
anime({
  targets: '.element',
  translateX: 250,
  easing: 'spring(1, 5000, 10, 2000)' // High stiffness and velocity
});

Test Plan

- All existing tests continue to pass
- New tests added for stiffness limits up to 10,000
- New tests added for velocity limits up to ±10,000
- Tests verify values above limits are properly clamped
- Tests confirm animations work with high parameter values
- Build process (npm run dev-types) works correctly
- Browser tests run successfully

Breaking Changes

None - this change is fully backward compatible.

Performance Impact

No performance regression expected. The change only increases upper
bounds while maintaining the same clamping behavior.

Closes #1039