[DOC] Add documentation for new OpenSearch Flow OSD plugin

[ohltyler]

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. Provide a summary of the request.
There is already backend documentation on the Flow Framework plugin (the backend plugin that powers this frontend plugin). Suggest to add documentation with an example, to show how to create a workflow for some sample use case, such as semantic search, via this new frontend plugin. This is already described in detail (with screenshots) in the tutorial. Perhaps some of the tutorial can be refactored / reused in the official documentation.

Target release date: 2.19

New APIs? No

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.
Tutorial: https://github.com/opensearch-project/dashboards-flow-framework/blob/main/documentation/tutorial.md
Repo / overview: https://github.com/opensearch-project/dashboards-flow-framework