[Feature Request]: Allow to customize the cache behavior in form visits

[hirasso]

Describe the problem 🧐

Currently, forms-plugin will always delete the cache of the target page before navigating towards it:

forms-plugin/src/index.ts

Lines 178 to 179 in 43d235c

	this.swup.cache.delete(action);
	this.swup.navigate(action + hash, params, { el, event });

This makes sense for most cases (search, contact forms, ...), but in other cases the cache might actually be useful. One example where I ran into this problem is a list that can be filtered by submitting a form:

https://example.com/users
https://example.com/users?filter=foo
https://example.com/users?filter=bar&sort=baz

Describe the propsed solution 😎

I'd like to make the cache controllable via the visit object. To reproduce the current behavior, this instantiation would make sense:

- this.swup.cache.delete(action);
- this.swup.navigate(action + hash, params, { el, event });
+const cache = {
+	read: false,
+	write: true
+};
+this.swup.navigate(action + hash, { ...params, cache }, { el, event });

That way, the consumer could decide if the request should make use of the cache or not (default: no cache):

swup.hooks.on("visit:start", (visit) => {
  if (visit.trigger.el?.matches('.my-filter-form')) {
    visit.cache.read = true;
  }
});

...or simply this if all requests should be cached:

swup.hooks.on("visit:start", (visit) => {
  visit.cache.read = true;
});

Alternatives considered 🤔

Not really an alternative that comes to mind. An attribute just for this would be pretty convoluted.

How important is this feature to you? 🧭

Would make my life a lot easier

Checked all these? 📚

• I have read and searched the official docs
• I have checked discussions and existing issues for related problems
• I agree to follow this project's Code of Conduct
• I have provided all necessary information to the best of my knowledge