feat: support deep partial props updates

[Tofandel]

This basically does a deep merge of the only props that have been requested using the dot notation (eg foo.baz) into the current props, instead of the current shallow merge

Goes by par with https://github.com/inertiajs/inertia-laravel/pull/435

[godismyjudge95]

This would be awesome. Exactly what I was talking about here: https://github.com/inertiajs/inertia/discussions/1249

[Tofandel]

@reinink Why would you Force push on master on a popular repo? You obliterated all the open PRs

[reinink]

Hey! Thanks so much for your interest in Inertia.js and for submitting this contribution.

In an attempt to get on top of the issues and pull requests on this project I am going through all the older issues and PRs and closing them, as there's a decent chance that they have since been resolved or are simply not relevant any longer. My hope is that with a "clean slate" me and the other project maintainers will be able to better keep on top of issues and PRs moving forward.

Of course there's a chance that this PR is still relevant, and if that's the case feel free to re-submit it. If it's a new feature and not a bug fix maybe respond here first to make sure that it's something we want to include in the library.

Really not trying to be dismissive here, I just need to find a way to get this project back into a state that I am able to maintain it. Hope that makes sense! ❤️