[improvement][config] Update datasource.properties，add mysql meta data template (#4266)

* Update datasource.properties

[新增]元数据mysql连接模版

* Update datasource.properties
Co-authored-by: Ndailidong <dailidong66@gmail.com>

dolphinscheduler-dao/src/main/resources/datasource.properties

@@ -21,6 +21,13 @@ spring.datasource.url=jdbc:postgresql://localhost:5432/dolphinscheduler
 spring.datasource.username=test
 spring.datasource.password=test
 
+# mysql
+#spring.datasource.driver-class-name=com.mysql.jdbc.Driver
+#spring.datasource.url=jdbc:mysql://127.0.0.1:3306/dolphinscheduler?useUnicode=true&characterEncoding=UTF-8
+#spring.datasource.username=xxxx
+#spring.datasource.password=xxxx
+
+
 # connection configuration
 #spring.datasource.initialSize=5
 # min connection number