Update microsite to docusaurus v2

[kriswest]

The https://fdc3.finos.org microsite is currently implemented with Docusaurus v1 and should be updated to Docusaurus v2, which will give us access to more Docusaurus plugins (e.g. render mermaid diagrams or client-side react) and more customisation options.

Migration docs:

• Migration guide
• Automated migration CLI
• Migrating versioned docs sites

Plugins:

• Official plugins
• Community plugins