Add DotProduct Method and README Example for Embedding Similarity Search (#492)

* Add DotProduct Method and README Example for Embedding Similarity Search

- Implement a DotProduct() method for the Embedding struct to calculate the dot product between two embeddings.
- Add a custom error type for vector length mismatch.
- Update README.md with a complete example demonstrating how to perform an embedding similarity search for user queries.
- Add unit tests to validate the new DotProduct() method and error handling.

* Update README to focus on Embedding Semantic Similarity

embeddings_test.go

@@ -4,7 +4,9 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
+	"math"
 	"net/http"
 	"reflect"
 	"testing"
@@ -233,3 +235,39 @@ func TestEmbeddingResponseBase64_ToEmbeddingResponse(t *testing.T) {
 		})
 	}
 }
+
+func TestDotProduct(t *testing.T) {
+	v1 := &Embedding{Embedding: []float32{1, 2, 3}}
+	v2 := &Embedding{Embedding: []float32{2, 4, 6}}
+	expected := float32(28.0)
+
+	result, err := v1.DotProduct(v2)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	if math.Abs(float64(result-expected)) > 1e-12 {
+		t.Errorf("Unexpected result. Expected: %v, but got %v", expected, result)
+	}
+
+	v1 = &Embedding{Embedding: []float32{1, 0, 0}}
+	v2 = &Embedding{Embedding: []float32{0, 1, 0}}
+	expected = float32(0.0)
+
+	result, err = v1.DotProduct(v2)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+
+	if math.Abs(float64(result-expected)) > 1e-12 {
+		t.Errorf("Unexpected result. Expected: %v, but got %v", expected, result)
+	}
+
+	// Test for VectorLengthMismatchError
+	v1 = &Embedding{Embedding: []float32{1, 0, 0}}
+	v2 = &Embedding{Embedding: []float32{0, 1}}
+	_, err = v1.DotProduct(v2)
+	if !errors.Is(err, ErrVectorLengthMismatch) {
+		t.Errorf("Expected Vector Length Mismatch Error, but got: %v", err)
+	}
+}