fix(refinement-list): re-apply focus on facet checkbox after render

[dhayab]

Summary

In InstantSearch.js, focus is lost when toggling a facet value in a refinement list. This is because the component is destroyed and re-created during re-render, and Preact does not explicitly refocus the newly created component (whereas React does it).

This PR adds code that stores the last refined value and applies focus to its DOM element on re-render.

CR-6976

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[Haroenv]

fix looks like a good workaround for now.

• is this happening anywhere else? What makes refinement list special that it doesn't need to be fixed somewhere else? no form elements in other components?
• test should be in CTS, maybe for all components?

[Haroenv]

I guess it won't matter if it happens anywhere else? focus can still be lost on a link right?

[dhayab]

is this happening anywhere else? What makes refinement list special that it doesn't need to be fixed somewhere else? no form elements in other components?

The loss of focus happens with all refinement widgets. I'm on the fence about adding this extra code to all widgets. It makes more sense for the refinement list as it allows proper toggling with the keyboard. Wdyt?