* use `Fragment` as the default element for `Transition` components
* update tests to reflect default tag change
* only error on missing `ref` if it's actually required
If the `<Transition />` component "root" is used as a root placeholder
(for state management) and not making actual transitions itself, then we
don't require a `ref` element.
* add test to ensure we don't error on missing `ref` when not required
+ add `className="…"` to some places to indicate that we _do_ want to
perform a transition and thus have to fail if the `ref` is missing.
* improve `requiresRef` check
Also ensure that a ref is required if the `as` prop is provided and
it's not a `Fragment`
* add `shouldForwardRef` helper
* fix broken tests
These tests were rendering a `Debug` element that didn't render any DOM
nodes. Adding `as="div"` ensures that we are forwarding the ref
correctly.
* update changelog
* update playgrounds to reflect tag change
* Tweak changelog
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Co-authored-by: Jonathan Reinink <jonathan@reinink.ca>
Robin Malfait
8fa5caf0dc