Add Hx-Swap header to the request

I have a situation where I want to change the behavior of my response to the client depending on the swap attribute.

I'm trying to develop a framework that uses HTMX and the user can define everything that is available in HTMX. This means that I can only know at the time of the request if the content should be swapped completely or if its only a partial replacement of the element.

It would make my life easier if the request also had an header like Hx-Target but with the swap value like Hx-Swap.

Edit: I've changed it to be an implementation in the getHeaders function and changed it according to the feedback from @scrhartley
[Fork dev branch](https://github.com/Declow/htmx/tree/add-hx-swap-header)

What do you think? Do you want to support this feature?