Add to docs that form data overrides hx-include inputs with the same name(s)

In the `getInputValues` function:

```
// form values take precedence, overriding the regular values
values = mergeObjects(values, formValues);
```

It would be neat if this detail was included in the [hx-include doc](https://htmx.org/attributes/hx-include/).

I had a group of inputs from another place in the DOM that were `hx-included` in a form issuing an hx-post request, and these extra inputs had the same name as some of the form's (which was intentional, I wanted a merging of the values in an array to happen) and could not figure out why they were not sent along with the request.

Thank you!