GitHub icon not focusing when tabbing in Safari

[GCHQ-Developer-465]

Summary of the bug

You can’t seem to focus/ tab onto the ‘GitHub’ icon in safari, but in chrome you can.

Note: Please test with as many folk as possible as this is often not repeated.

🪜 How to reproduce

Tell us the steps to reproduce the problem:

1. Go to page landing page
2. Tab through the site
3. See the error (just tabbing focus until Search bar)

📸 Screenshots or code

🖥 📱 Device

• Browser version: [Safari]

🧐 Expected behaviour

You should be able to focus on the GitHub Icon like in Chrome.