Adds rel parameter to the social icons configuration documentation

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Prerequisites

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• This pull request fixes a bug.
• This pull request adds a feature.
• This pull request introduces breaking change.

Description

PR #195 added the rel parameter to the social icons configuration. This addition is missing in the documentation

Issues Resolved

This PR adds the parameter to the list for the social icons configuration in the documentation (configuration.md)

Checklist

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General

• Describe what changes are being made
• Explain why and how the changes were necessary and implemented respectively
• Reference issue with #<ISSUE_NO> if applicable

Resources

• If you have changed any SCSS code, run make release to regenerate all CSS files

Contributors

• Add yourself to CONTRIBUTORS.md if you aren't on it already