[DOC] Incorrect docs on creating non dynamic index mapping

[Avinash-B]

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.
OpenSearch documentation of creating explicit indexes do not warn users that OpenSearch dynamically adds new data members and types in the index. Request to add more details related to this and usage of dynamic keyword in index mapping.

What other resources are available?

• https://opensearch.org/docs/latest/field-types/index/#explicit-mapping
• https://www.elastic.co/guide/en/elasticsearch/reference/current/dynamic-field-mapping.html