Fix security issues in website javascript

The change to pnmp triggered a large number of security alerts from dependabot.

7 could be fixed directly by the 4 PRs opened by dependabot. 6 need manual intervention.

The change also included an upgrade of the Algolia search component to 3.x. That change prevent running pnpm audit.
Docusaurus 3.x also contains a large number of backward incompatible changes and an upgrade is planned separately. Using the Algolia 3.x dependency already pushes some of these changes and should be reverted to Algolia 2.x same as the rest of Docusaurus environment.