Investigate use of reactive controllers for observers

[Niznikr]

The problem Within Pharos there is usage of MutationObservers and ResizeObservers that can be modularized to reuse such features more easily.

The solution Use Lit's reactive controllers to improve reusability of observers across multiple components.

[Niznikr]

A package is in development by Lit to add controllers for common observers.

[Niznikr]

The package has been released and an example can be found on its blog post.