Added additional_messages (#914)

run.go

@@ -87,6 +87,7 @@ type RunRequest struct {
 	Model                  string          `json:"model,omitempty"`
 	Instructions           string          `json:"instructions,omitempty"`
 	AdditionalInstructions string          `json:"additional_instructions,omitempty"`
+	AdditionalMessages     []ThreadMessage `json:"additional_messages,omitempty"`
 	Tools                  []Tool          `json:"tools,omitempty"`
 	Metadata               map[string]any  `json:"metadata,omitempty"`