feat: toggle refinement styling

[thomasbritton]

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[sarahdayan]

I'm not sure why we need such selector, why not target .ais-ToggleRefinement-checkbox?

[thomasbritton]

This is because there is a selector in common.css that is of higher specificity input[class^='ais-'][type='checkbox']:checked { /* ... */ }

I did it this way because we were out of time so just needed something quick that would work but the class above probably needs to be merged into the refinement-list.css

[thomasbritton]

@sarahdayan I have re-worked so it uses the default class name .ais-ToggleRefinement-checkbox

[Haroenv]

Do you still want this merged in the base branch or restart when this project continues?