Improve the mike workflow

[Ludee]

Summary of the discussion

Describe the findings of the discussion in the issue or meeting.

Type of change (CHANGELOG.md)

Added

• Add a favicon for the documentation (54#)
• Add a warning for older versions that links to latest (#54)

Changed

• Update CSS to improve toc (#54)
• Update documentation for mike (#54)

Removed

• Disable GitHub Action for MkDocs Workflow (#54)

Workflow checklist

Automation

Closes #36

PR-Assignee

• 🐙 Follow the workflow in CONTRIBUTING.md
• 📝 Update the CHANGELOG.md
• 📙 Update the documentation

Reviewer

• 🐙 Follow the Reviewer Guidelines
• 🐙 Provided feedback and show sufficient appreciation for the work done