[DOC] Update documentation for Using Search Pipeline

[owaiskazi19]

What do you want to do?

• [x] Request a change to existing documentation
• [x] Add new documentation
• [ ] Report a technical problem with the documentation
• [ ] Other

Tell us about your request. Provide a summary of the request and all versions that are affected. Search Pipeline will support default pipeline for multiple indices in 2.14. Issue: https://github.com/opensearch-project/OpenSearch/issues/7512 PR: https://github.com/opensearch-project/OpenSearch/pull/13276

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.

[minalsha]

@owaiskazi19 is the POC. @hdhalter requesting support for documentation for this enhancement. Thanks

[hdhalter]

Thanks, @owaiskazi19 !