Feature / add link target support

[mpertici-beapi]

Summary

• Add a targetBlank block attribute (default false) and an "Open in a new tab" toggle in the link URL popover.
• Render target="_blank" with rel="noopener noreferrer" on the front end when enabled.
• Improve link toolbar UX: separate Edit / Remove actions when a link is set; reset targetBlank on remove.
• Cover targetBlank behavior with PHPUnit cases in BlockRendererTest.

Test plan

• Add a link on an icon block → confirm the popover shows the URL field and the "Open in a new tab" toggle
• Enable the toggle → save → front end has target="_blank" and rel="noopener noreferrer"
• Disable the toggle (or leave it off) → front end has neither target nor rel
• With a link set, toolbar shows Edit link and Remove link; removing clears URL and targetBlank
• Without a URL, no <a> is rendered even if targetBlank is true
• Run composer test / PHPUnit and confirm the new BlockRendererTest cases pass

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Note

Low Risk
Scoped to icon link rendering and editor UX; uses standard rel="noopener noreferrer" for external targets with existing URL escaping unchanged.

Overview
Adds optional open in a new tab for icon block links via a new targetBlank attribute (default false).

Editors get an Open in a new tab toggle in the link URL popover; when enabled, front-end markup includes target="_blank" and rel="noopener noreferrer". Link toolbar behavior changes when a URL is set: separate Edit link and Remove link actions, and removing a link clears both url and targetBlank. The popover layout is restyled so the URL row and toggle stack cleanly.

PHPUnit coverage asserts when target/rel appear or stay absent, including the case where targetBlank is true without a URL (no anchor rendered).

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