Add sparse embedding models to list of compatible models

[davidkyle]

With the change in elastic/eland#740 Eland now supports uploading 3rd party sparse embedding models (other than ELSER). This PR adds some models to the list of known compatible models.

The Eland command to install one of these models must use the text_expansion task type

eland_import_hub_model \
      --url 'http://localhost:9200' \
      -u elastic-admin -p elastic-password \
      --hub-model-id 'hotchpotch/japanese-splade-base-v1' \
      --task-type text_expansion 

[github-actions]

A documentation preview will be available soon.

• 🔨 Buildkite builds
• 📚 HTML diff
• 📙 Preview page

Request a new doc build by commenting

• Rebuild this PR: run docs-build
• Rebuild this PR and all Elastic docs: run docs-build rebuild

_{run docs-build is much faster than run docs-build rebuild. A rebuild should only be needed in rare situations.}

_{If your PR continues to fail for an unknown reason, the doc build pipeline may be broken. Elastic employees can check the pipeline status here.}

[szabosteve]

Thank you for this addition, LGTM!

[daixque]

LGTM, but just dropped one comment.

[szabosteve]

LGTM!