[IMPROVEMENT] Improved navbar and usage of absolute links to icons using site-urls

Description

This MR improves the website layout by incorporating multiple elements: Improvement navbar:

• sizing.md, analysis.md and libraries.md are now removed from the documentation folder and placed at the sizing, analysis and libraries folder as index.md → this makes use of navbar.indexes since there is no necessity for the overview pages anymore which are directly linked now to sizing, analysis and libraries.
• added sticky tabs to keep visible while scrolling
• enabled toc.follow to follow the toc while scrolling (right side)

Related Issue(s)

None

Other Changes

Fixed download page -> was getting_started.md not getting-started.md

Screenshots/Logs

Testing Instructions

Checked locally

Developer Checklist

• Code has been tested locally.
• Minor check was conducted - seems to work properly
• Todo → major check with pipeline.

Additional Notes

Please make sure that the mkdocs site-urls plugin is installed via pipeline. I have it locally installed.