Feature: support overriding form behavior from submitter element

[daun]

Describe the problem

HTML allows overriding the form action, method and target from the submit button itself. Clicking the first submit button will submit a GET request, clicking the second button will submit to /search:

<form action="/" method="POST">
  <input type="submit" formmethod="GET" value="Submit as GET">
  <input type="submit" formaction="/search" value="Submit to /search">
</form>

Describe the proposed solution

Check for the SubmitEvent's submitter property and deduce the final form behavior from there, if present.

Alternatives considered

None, really, if we want to comply to current standards

How important is this feature to you?

• Nice to have
• Would make my life a lot easier
• I cannot use swup without it