Spring Modernize Antora Build - Nineya|java/go/python

Use package.json so dependabot can automatically update JS dependencies
Use @springio/antora-extensions (automatically apply default extensions in proper order)
Leverage set-algolia-env-extension to manage algolia env variables
Update to latest ui

Comment From: sdeleuze

I am not able to merge this one due to the following error:

[10:37:39.263] FATAL (antora) <git.readBlob>: Cannot read properties of null (reading 'slice') in https://github.com/spring-projects/spring-framework (tag: v6.0.10 | start path: framework-docs)
    Cause: TypeError
        at GitPackIndex.readSlice (/Users/sdeleuze/workspace/spring-framework-branches/docs-build/node_modules/@antora/content-aggregator/node_modules/isomorphic-git/index.cjs:2974:35)
        at async readObjectPacked (/Users/sdeleuze/workspace/spring-framework-branches/docs-build/node_modules/@antora/content-aggregator/node_modules/isomorphic-git/index.cjs:3091:22)
        at async _readObject (/Users/sdeleuze/workspace/spring-framework-branches/docs-build/node_modules/@antora/content-aggregator/node_modules/isomorphic-git/index.cjs:3133:14)
        at async resolveBlob (/Users/sdeleuze/workspace/spring-framework-branches/docs-build/node_modules/@antora/content-aggregator/node_modules/isomorphic-git/index.cjs:12507:28)
        at async _readBlob (/Users/sdeleuze/workspace/spring-framework-branches/docs-build/node_modules/@antora/content-aggregator/node_modules/isomorphic-git/index.cjs:12550:16)
        at async Object.readBlob (/Users/sdeleuze/workspace/spring-framework-branches/docs-build/node_modules/@antora/content-aggregator/node_modules/isomorphic-git/index.cjs:12609:12)
        at async Promise.allSettled (index 2)
        at async Promise.allSettled (index 0)
        at async Promise.allSettled (index 2)

I am wondering if it is required I wait for our new releases with #32864 merged, and fine tune the branches in this PR to use minimum tags 6.0.21 and 6.1.8 in order to avoid such breakage.

I am also wondering if we can now remove lib/antora/templates/per-branch-antora-playbook.yml.

Comment From: sdeleuze

Merged. The error was due to a corrupted local Antora cache. I have removed per-branch-antora-playbook.yml after discussing with Rob.