PIP-87: Upgrade Pulsar Website Framework (Docusaurus)

• Status: accepted
• Author: Anonymitaet
• Contributor: Anonymitaet, urfreespace, zeo1995 (feel free to add your names if missing)
• Issue: click here
• Mailing list discussion: we have many discussions, the earliest one is here.
• Design proposal, discussion, implementation progress, and all details: click here