Add example for the new ECS console appender for spring boot

Author: ipalbeniz

docs/tab-widgets/ecs-encoder.asciidoc

@@ -11,8 +11,10 @@ In `src/main/resources/logback-spring.xml`:
     <include resource="org/springframework/boot/logging/logback/defaults.xml"/>
     <include resource="org/springframework/boot/logging/logback/console-appender.xml" />
     <include resource="org/springframework/boot/logging/logback/file-appender.xml" />
+    <include resource="co/elastic/logging/logback/boot/ecs-console-appender.xml" />
     <include resource="co/elastic/logging/logback/boot/ecs-file-appender.xml" />
     <root level="INFO">
+        <appender-ref ref="ECS_JSON_CONSOLE"/>
         <appender-ref ref="CONSOLE"/>
         <appender-ref ref="ECS_JSON_FILE"/>
         <appender-ref ref="FILE"/>