Docs: missing assets & configuration

[jbroma]

Summary

Tracking issues for missing assets & configuration for documentation

• - open graph image - og-image.png
• - site Icon - icon.ico
• - configured CTA link for Home Banner
• - configured CTA link for Contents sidebar
• - configured CTA link for Doc page footer
• - configured home footer link

[grabbou]

Performed some tweaks regarding points 3-6 in callstack/rspress-theme#80. Will update OG Image and Favicon later.