[docs] Add checkpoint config in document example

docs/content/connectors/mysql-cdc.md

@@ -71,25 +71,28 @@ How to create a MySQL CDC table
 The MySQL CDC table can be defined as following:
 
 ```sql
--- register a MySQL table 'orders' in 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 (
-  'connector' = 'mysql-cdc',
-  'hostname' = 'localhost',
-  'port' = '3306',
-  'username' = 'root',
-  'password' = '123456',
-  'database-name' = 'mydb',
-  'table-name' = 'orders');
+-- checkpoint every 3000 milliseconds                       
+Flink SQL> SET 'execution.checkpointing.interval' = '3s';   
 
+-- register a MySQL table 'orders' in Flink SQL
+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 (
+     'connector' = 'mysql-cdc',
+     'hostname' = 'localhost',
+     'port' = '3306',
+     'username' = 'root',
+     'password' = '123456',
+     'database-name' = 'mydb',
+     'table-name' = 'orders');
+  
 -- read snapshot and binlogs from orders table
-SELECT * FROM orders;
+Flink SQL> SELECT * FROM orders;
 ```
 
 Connector Options
@@ -376,7 +379,8 @@ public class MySqlBinlogSourceExample {
       .build();
 
     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