Move code for favicons to its own file

[Vulcalien]

What does this PR change? What problem does it solve?
It moves the code for including favicons from the head.html to the favicons.html partial. This allows the user to specify his own code for favicons overriding the favicons.html file instead of all of head.html.

Was the change discussed in an issue or in the Discussions before?
I don't think this exact change has been proposed yet.

PR Checklist

• This change adds/updates translations and I have used the template present here.
• I have enabled maintainer edits for this PR.
• I have verified that the code works as described/as intended.
• This change adds a Social Icon which has a permissive license to use it.
• This change does not include any CDN resources/links.
• This change does not include any unrelated scripts such as bash and python scripts.
• This change updates the overridden internal templates from HUGO's repository.

[sonarcloud]

Quality Gate passed

Issues
0 New issues

Measures
0 Security Hotspots
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarCloud