Publish airgapped image using stripped down preview server

[Mpdreamz]

This moves our air-gaped image away from ./docs-build.pl and use the preview/cli.js directly.

This preview server is needed because it uses the embedded raw git database to read files directly from git's blob database.

This adds a new package.json that is used to restore preview and template in isolation limiting the dependency graph.

This allows us to run on the latest nodejs after replacing unsafe usages of url.parse with modern equivalents.

The image can be build locally using:

docker build -t docker.elastic.co/docs-private/bk_air_gapped_wolfi:latest -f air_gapped/Dockerfile .

docker run -a STDERR -a STDOUT -i --rm \
              --publish 3000:3000 \
              docker.elastic.co/docs-private/bk_air_gapped_wolfi:latest

Output from CVE scanning using:

docker scout cves local://docker.elastic.co/docs-private/bk_air_gapped_wolfi:latest

[github-actions]

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