Implement CSS Getters and Setters, Resize Event Handler Fix, Enhanced Element Position Detection, Refactoring, and Cleanup (#647). Introduces several improvements and fixes as follows:

1. Utilize CSS getters and setters:

   • This update enhances the library's usage of CSS getters and setters for improved performance and compatibility.

2. Fix resizing event handler:

   • Addressed a bug in the resizing event handler that failed to trigger the expected chain of updaters related to the event. This fix ensures that the chain of updaters is correctly executed.

3. Enhanced element position detection:

   • Introduced a unified logic to detect an element's position relative to the viewport. This enhancement provides a more consistent and accurate position calculation.

4. Remove the optional object for setting the inner scroll threshold:

   • Eliminated the need for an optional object parameter when setting the inner scroll threshold. This simplifies the API and improves code readability.

5. Refactor and remove unnecessary methods in the Threshold class:

   • Streamlined the Threshold class by removing unnecessary methods and increasing reliance on the Box model. This refactoring improves code efficiency and maintainability.

Migrate related box model in Threshold to the Box Model (#646): Focuses on migrating the related box model present in the threshold to the Box model. The aim is to consolidate the codebase and improve consistency. Allowing better modularization, and enhancing code maintainability and readability.