A general remix's headers handler

[nichtsam]

I noticed that epic-stack doesn't have utils like reuseUsefulLoaderHeaders that Kent has on kentcdodds.com.
I thought it'd be a nice thing to have, it's kind of a pain to manage all that headers stuff, so I integrated it into my project with some modifications.
It has been working nicely on my project for a while already, and I thought that epic-stack might be able to benefit from this.

Here is the gist for the code I've been using:
https://gist.github.com/nichtsam/bff3a0e58f7edfad3985e9322582f67f

[kentcdodds]

Thanks @nichtsam! I think that could be useful as well. I am open to a PR!

[nichtsam]

PR opened! #810