Fix wcag keyboard modal cookie settings

[BarbaraOliveira13]

🎩 What?

Updated the cookie settings modal trigger in the footer by adding role="button" to the <a> tag.

🎩 Why?

Insure the <a> tag behave like a button for an interactive action that opens a modal, expected by assistive technologies:

• Enhances accessibility by natively supporting keyboard interactions like TAB + ENTER and TAB + SPACE

📌 Related Issues

• WCAG Criterion: 4.1.2 - Name, Role, Value
• WCAG Criterion: 2.1.1 - Keyboard Accessibility
• Grist Diagnostique Decidim - Line 6
• Decidim Issue
• Update from first PR RGAA

📋 Steps to Test

1. Navigate to any page with the footer.
2. Focus on the "Data Consent Settings" button using TAB:

• With VoiceOver (macOS) or NVDA (Windows) activated verify that the modal opens correctly when you : Press SPACE or ENTER to open the modal.
• Inspect and verify that the <a> tag as role="button"

📋 Subtasks

• Added role="button" to the tag.
• Confirmed keyboard interactions (SPACE/ENTER) work as expected.

📷 Screenshots (optional)

Additional Context

This update improves compliance with WCAG accessibility standards and enhances the user experience for those navigating via keyboard or assistive technologies.

[AyakorK]

LGTM !