Add social media icons row to footer

[Copilot]

Description

Adds a row of social media icons (Newsletter, GitHub, X) positioned above the copyright section in the footer with actual URLs and Font Awesome 6.5.1 icons.

Changes

• _includes/footer.html: Added footer-social-icons div with three Font Awesome 6.5.1 icon links (envelope, github, x-twitter) between footer columns and copyright
• _sass/_layout.scss: Added styles for centered horizontal layout with 15px spacing, hover/focus states, and color transitions
• Merged from main: Updated to use Font Awesome 6.5.1 from CDN

Implementation Details

• Uses Font Awesome 6.5.1 icons from CDN (2x size for visibility)
• Newsletter: fa-solid fa-envelope → https://testingconferences.us11.list-manage.com/subscribe?u=2a811daec24cc97909dfdf01d&id=88f87313fc
• GitHub: fa-brands fa-github → https://github.com/TestingConferences/testingconferences.github.io
• X/Twitter: fa-brands fa-x-twitter (latest X icon) → https://x.com/testconferences
• Links include rel="noopener noreferrer" for security
• Accessible with aria-label, title attributes, and keyboard focus styles

Checklist

• Changes follow existing footer styling patterns
• HTML validated
• Security scan passed
• Code review feedback addressed
• Merged latest from main branch
• Updated to Font Awesome 6.5.1 icons with latest X icon

Screenshot

Original prompt

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This section details on the original issue you should resolve

<issue_title>Footer Content Updates</issue_title>
<issue_description>Add a row of Social Icons / Links just above the copyright section.

1. Link to MailChimp Newsletter
2. Link to GitHub Account
3. Link to X Account
4. All links should be on one row</issue_description>

<agent_instructions>If you don't know the links, just make the urls "example.com"</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes Footer Content Updates #337

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[ckenst]

@copilot let's make a few changes:

1. Get the latest from main
2. Use the latest X icon for Twitter/X from font-awesome (this already exists in the repo)
3. Join our newsletter link: https://testingconferences.us11.list-manage.com/subscribe?u=2a811daec24cc97909dfdf01d&id=88f87313fc
4. GitHub link: https://github.com/TestingConferences/testingconferences.github.io
5. Twitter/X link: https://x.com/testconferences

[Copilot]

@copilot let's make a few changes:

1. Get the latest from main
   ...

Done! Changes made in commit 544d306:

1. ✅ Merged latest from main branch
2. ✅ Updated to Font Awesome 6.5.1 with the latest X icon (fa-brands fa-x-twitter)
3. ✅ Updated newsletter link to https://testingconferences.us11.list-manage.com/subscribe?u=2a811daec24cc97909dfdf01d&id=88f87313fc
4. ✅ Updated GitHub link to https://github.com/TestingConferences/testingconferences.github.io
5. ✅ Updated X link to https://x.com/testconferences