Missing focus style for the 'Choose a pattern' modal dialog listbox options

[afercia]

Description

Keyboard users need a visible focus style to see where focus is and consequently be able to use an user interface. This is a basic requirement for accessibility and usability.

When creating a new template in the site editor, the preview options in the 'Choose a pattern' modal dialog do have a hover style:

but they don't have a focus style:

Turns out in the related stylesheet there's a :focus rule but it's applied to an element that is not focusable....

Step-by-step reproduction instructions

• Go to the site editor.
• Create a new custom template.
• Wait.
• The 'Choose a pattern' modal dialog opens.
• Hover your mouse on the available patterns previews and observe there's a hover style.
• Use the Tab key to navigate through the focusable elements within the modal and observe the patterns previews don't have a focus style.

Screenshots, screen recording, code snippet

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Environment info

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Please confirm that you have searched existing issues in the repo.

Yes

Please confirm that you have tested with all plugins deactivated except Gutenberg.

Yes