Upgrade docs.neos.io to Neos 9

[ahaeslich]

The Docs should be a good first project to update to Neos9

[Jan3k3y]

The following packages are included and are compatible (✔️) or not (❌):
💡 PR created
🛑 will not be updated/part of docs in future

DistributionPackage:
✔️ neos/neos (9.0.0-beta1)
✔️ neos/neos-ui (9.0.0-beta1)
✔️ neos/nodetypes-contentreferences (9.0.0-beta1)
✔️ neos/redirecthandler-ui (3.0.0)
✔️ neos/redirecthandler-neosadapter (5.0.0)
✔️ neos/redirecthandler-databasestorage (6.0.0)
✔️ neos/seo (4.0.0)
🛑 aertmann/history (neos/neos: >3 )
💡 codeq/publishnotifier (Draft PR still missing some features, but neos 9 compatible)
🛑 codeq/htmlwidget (not used anymore)
❌ carbon/compression (will be kicked out maybe)
❌ carbon/link (2.0.0)
❌ carbon/includeassets (6.0.0)
✔️ flowpack/cachebuster (1.3.0)
💡 flowpack/nodetemplates (PR to add Neos 9 compatibility)
❌ flowpack/neos-matomo
❌ flowpack/searchplugin
❌ flowpack/media-ui (restructured and not needed?)
❌ flowpack/elasticsearch-contentrepositoryadaptor (exchange with sandstorm/LightweightElasticsearch?)
🛑 sitegeist/silhouettes (remove -> was moved into neos core in 7.0)
❌ sandstorm/mxgraph (can be installed because it allows dev-master, but php code is not actually compatible)
❌ yoast/yoast-seo-for-neos
❌ jonnitto/prettyembedvideoplatforms (Sophia is working on it)

❌jonnitto/prettyembedhelper

✔️sitegeist/slipstream (with dev-main, still needs official version)
✔️carbon/fileloader (0.1.5)
✔️carbon/notification (3.0.0)
✔️carbon/eel (2.5.0) -> please check again

✔️ shel/neos-hyphens (PR to add Neos 9 compatibility -> merged. Use main)
🛑 shel/neos-workspace-module (will be moved to the neos core)

Project:
✔️ flownative/google-cloudstorage (v6.0.0-beta.2)
❌ rokka/imagine-vips
❌ shel/neos-terminal (Runa is working on it)
✔️ jcupitt/vips (*)

Project-Dev:
✔️ roave/security-advisories (*)
🛑 t3n/neos-debug (replace with flowpack/neos-debug)