Improve referenced doc navigation

Signed-off-by: Christian Tzolov <[email protected]>

Author: tzolov

spring-ai-docs/src/main/antora/modules/ROOT/nav.adoc

@@ -89,21 +89,21 @@
 ** xref:api/vectordbs/typesense.adoc[]
 ** xref:api/vectordbs/weaviate.adoc[]
 
-* xref:api/retrieval-augmented-generation.adoc[]
-* xref:observability/index.adoc[]
-* xref:api/prompt.adoc[]
+* xref:api/retrieval-augmented-generation.adoc[Retrieval Augmented Generation (RAG)]
+** xref:api/etl-pipeline.adoc[]
 * xref:api/structured-output-converter.adoc[Structured Output]
 * xref:api/tools.adoc[Tool Calling]
-* xref:api/functions.adoc[Function Calling (Deprecated)]
-** xref:api/function-callback.adoc[FunctionCallback API (Deprecated)]
 ** xref:api/tools-migration.adoc[Migrating to ToolCallback API]
 * xref:api/mcp/mcp-overview.adoc[Model Context Protocol (MCP)]
 ** xref:api/mcp/mcp-client-boot-starter-docs.adoc[MCP Client Boot Starters]
 ** xref:api/mcp/mcp-server-boot-starter-docs.adoc[MCP Server Boot Starters]
 ** xref:api/mcp/mcp-helpers.adoc[MCP Utilities]
 * xref:api/multimodality.adoc[Multimodality]
-* xref:api/etl-pipeline.adoc[]
+* xref:observability/index.adoc[]
+* xref:api/prompt.adoc[]
 * xref:api/testing.adoc[AI Model Evaluation]
+* xref:api/functions.adoc[Function Calling (Deprecated)]
+** xref:api/function-callback.adoc[FunctionCallback API (Deprecated)]
 
 * Service Connections
 ** xref:api/docker-compose.adoc[Docker Compose]