Expose styles to be reused

[JaredP17]

Thanks for the continued support of this library! In a review comment I got at work I was asked where I got the color hex values from to match the loadingElement custom component with the rest of the diff viewer styles.

Problem: Custom components (like loadingElement) lack access to the library's internal theme, leading to inconsistent UI or fragile, hardcoded styles.

Proposed Solution: Export the defaultStyles or theme object so it can be consumed by custom renderers.