Ignore formmethod when value is "dialog"

[SamDudley]

In the following example htmx will issue a DIALOG request instead of a POST request.

<dialog>
    <form hx-post="/test">
        <button formmethod="dialog" name="foo" value="bar">Submit</button>
    </form>
</dialog>

This PR changes the behaviour so that htmx will issue a POST request.

Closes #1866

[alexpetros]

Heads up that I don't think you tagged the right issue in the description (I updated it).

Otherwise, good catch, thanks for the PR.

[pokonski]

Hey, @SamDudley . According to MDN and what I observed, such forms should never be submitted to the backend at all:

When a <form> within a <dialog> is submitted via the dialog method, the dialog box closes, the states of the form controls are saved but not submitted,

https://developer.mozilla.org/en-US/docs/Web/HTML/Element/dialog

Also their example code does mention this again:

So the method should not be changed, but submit completely skipped

[SamDudley]

Hey @pokonski, I've left a comment on #2753 discussing this issue. In short, I agree that my change is inconsistent with the MDN docs and support it being changed.