Docusaurus 3.5.x and MDX 3 migration

[lhotari]

Motivation

• current website dependencies are outdated and need to be updated
• this update enables to continue evolving the website without being blocked by old versions

Changes

• followed https://docusaurus.io/docs/migration/v3 MDX v3 is more strict and that's why content updates were needed
  • Common MDX problems covers the issues
• replaced {@inject: ... } implementation with a Docusaurus markdown preprocessor since remark-linkify-regex no longer works since MDX v3 AST has changed.
• Since validation is more strict, fixed a lot of content issues such as missing Tabs on a few pages.
• Updated customized theme components by swizzling them again and diffing the customizations (upgrade instructions)

✅ Contribution Checklist

• I read the contribution guide
• I updated the versioned docs

[lhotari]

pushed 5805228 to fix a regression in the mobile / responsive layout for narrow display widths. The css class of the searchbox had changed.