[DOC] Query Insights Dashboards Documentation

[ansjcy]

What do you want to do?

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

Tell us about your request.
We are introducing query insights dashboards in 2.19 and need to add documentation for frontend.
See: https://github.com/opensearch-project/query-insights-dashboards

Version: List the OpenSearch version to which this issue applies, e.g. 2.14, 2.12--2.14, or all.
2.19

What other resources are available? Provide links to related issues, POCs, steps for testing, etc.
https://github.com/opensearch-project/query-insights-dashboards