feat: add JsonObjectNode merge

[gioboa]

Summary

This PR add JsonObjectNode merge method.
Remove any existing destination properties that clash with source, along with their leading/trailing trivia, to avoid duplicate keys.

• Close comments lost while merging #6

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have checked my code and corrected any misspellings

[marcospassos]

Hey @gioboa, thanks a lot for the contribution!

I've made a few updates to the API, the main one is turning it into an instance method instead of a static one, so usage now looks like:

destination.merge(source)

I also handled several edge cases and added some logic to make the merging feel more natural. For example, trailing comments are now moved along with the destination property, since they usually belong to the preceding key.

[gioboa]

Thanks, that's fine to me 💯