[docs] Add checkpoint config in document example

docs/content/connectors/mysql-cdc.md

@@ -71,15 +71,18 @@ How to create a MySQL CDC table
 The MySQL CDC table can be defined as following:
 
 ```sql
+-- checkpoint every 3000 milliseconds                       
+Flink SQL> SET 'execution.checkpointing.interval' = '3s';   
+
 -- register a MySQL table 'orders' in Flink SQL
-CREATE TABLE orders (
+Flink SQL> CREATE TABLE orders (
      order_id INT,
      order_date TIMESTAMP(0),
      customer_name STRING,
      price DECIMAL(10, 5),
      product_id INT,
      order_status BOOLEAN
-) WITH (
+     WITH (
      'connector' = 'mysql-cdc',
      'hostname' = 'localhost',
      'port' = '3306',
@@ -89,7 +92,7 @@ CREATE TABLE orders (
      'table-name' = 'orders');
   
 -- read snapshot and binlogs from orders table
-SELECT * FROM orders;
+Flink SQL> SELECT * FROM orders;
 ```
 
 Connector Options
@@ -377,6 +380,7 @@ public class MySqlBinlogSourceExample {
 
     StreamExecutionEnvironment env = StreamExecutionEnvironment.getExecutionEnvironment();
     
+    env.enableCheckpointing(3000); // checkpoint every 3000 milliseconds
     env
       .addSource(sourceFunction)
       .print().setParallelism(1); // use parallelism 1 for sink to keep message ordering