Updating writeJSON helper method replacing json.Marshal() by json.MarshalIndent() method to improve responses readability. Updating README adding Performance sub-section.

cmd/api/helpers.go

@@ -49,8 +49,11 @@ http.ResponseWriter, the HTTP status code to send, the data to encode to JSON, a
 header map containing any additional HTTP headers we want to include in the response.
 */
 func (app *application) writeJSON(w http.ResponseWriter, status int, data any, headers http.Header) error {
-	// Encode the data to JSON, returning the error if there was one.
-	js, err := json.Marshal(data)
+	/*
+		Use the json.MarshalIndent() function so that whitespace is added to
+		the encoded JSON. Here we use no line prefix ("") and tab indents ("\t") for each element.
+	*/
+	js, err := json.MarshalIndent(data, "", "\t")
 	if err != nil {
 		return err
 	}