embeddings: add example of proper usage, and tweak doc.go accordingly

For #379

embeddings/doc.go

@@ -1,15 +1,14 @@
 /*
-Package embeddings contains the implementation for creating vector
-embeddings from text using different APIs, like OpenAI and Google PaLM (VertexAI).
+Package embeddings contains helpers for creating vector embeddings from text
+using different providers.
 
 The main components of this package are:
 
-- Embedder interface: a common interface for creating vector embeddings from texts.
-- OpenAI: an Embedder implementation using the OpenAI API.
-- VertexAIPaLM: an Embedder implementation using Google PaLM (VertexAI) API.
-- Helper functions: utility functions for embedding, such as `batchTexts` and `maybeRemoveNewLines`.
+  - [Embedder] interface: a common interface for creating vector embeddings
+    from texts, with optional batching.
+  - [NewEmbedder] creates implementations of [Embedder] from provider LLM
+    (or Chat) clients.
 
-The package provides a flexible way to handle different APIs for generating
-embeddings by using the Embedder interface as an abstraction.
+See the package example below.
 */
 package embeddings

embeddings/example_test.go

@@ -0,0 +1,30 @@
+package embeddings_test
+
+import (
+	"context"
+	"log"
+
+	"github.com/tmc/langchaingo/embeddings"
+	"github.com/tmc/langchaingo/llms/openai"
+)
+
+func Example() {
+	llm, err := openai.New()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	embedder, err := embeddings.NewEmbedder(llm)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	docs := []string{"doc 1", "another doc"}
+	embs, err := embedder.EmbedDocuments(context.Background(), docs)
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	// Consume embs
+	_ = embs
+}