Change headlessui library

[jamesscottbrown]

What does this change?

Why?

How?

Related issues:

Does this introduce new dependencies?

How is it tested?

How is it documented?

Are light and dark themes considered?

Is it complete?

• [ ] Have you included changeset file?
• [ ] If this adds a new component, is it exported via index.js?

[jamesscottbrown]

Some thoughts:

• like the example, this uses svelte-transition to transition the opacity of the modal between 0 and 100. We haven't yet given much thought to either what animated transitions should be used in our design system, or whether we should use a library like svelte-transition to implement them
• this changes the API of the modal component, from exposing an isOpen Boolean, to exposing an object with .open() and .close() methods
• is this the best headless UI library for us to use, or should we consider using Melt UI instead?

[ChrisKnightLDN]

Melt-ui looks interesting I'd like to try it out

[ChrisKnightLDN]

Closing in favour of pursuing melt-ui