[DOCS] Create open API specifications for the case APIs

[lcawl]

Summary

Copy the layout used in https://github.com/elastic/kibana/tree/main/x-pack/plugins/fleet/common/openapi to model the following APIs:

• Add comment Adds OpenAPI specs for case comment endpoints #133400
• Create case Add openAPI specifications for cases endpoint #131275
• Delete case Add openAPI specifications for cases endpoint #131275
• Delete comments Adds OpenAPI specs for case comment endpoints #133400
• Find cases Add openAPI specifications for cases _find endpoint #131761
• Find connectors Add open API specification for find connector #133840
• Get alerts [DOCS] Adds openAPI spec for get alerts endpoint #137332
• Get case activity Add open API specification for get case activity #136465
• Get cases Add open API specification for get case API #136315
• Get case status Adds OpenAPI spec for get case status #136128
• Get case configuration Add openAPI specifications for cases configure endpoint #133265
• Get cases by alert Add openAPI specifications for cases configure endpoint #133265
• Get comments Add openAPI specifications for get comments API #135921
• Get reporters [DOCS] Add get reporters to open API spec #135326
• Get tags Add openAPI specifications for get tags API #135671
• Push case Add openAPI specifications for push case API  #137549
• Set case configuration Add openAPI specifications for cases configure endpoint #133265
• Update case Add openAPI specifications for cases endpoint #131275
• Update comment Adds OpenAPI specs for case comment endpoints #133400
• Update case configuration Add openAPI specifications for cases configure endpoint #133265

The specifications will be stored in the following folder: https://github.com/elastic/kibana/tree/main/x-pack/plugins/cases/docs/openapi

[elasticmachine]

Pinging @elastic/kibana-docs (Team:Docs)

[elasticmachine]

Pinging @elastic/response-ops-cases (Feature:Cases)