Initial graylog + spring boot demo (#5299)

* Initial graylog + spring boot demo

* Move Graylog demo into existing spring-boot module

spring-boot/src/main/java/com/baeldung/graylog/GraylogDemoApplication.java

@@ -0,0 +1,17 @@
+package com.baeldung.graylog;
+
+import org.apache.log4j.Logger;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+
+@SpringBootApplication
+public class GraylogDemoApplication {
+
+    private final static Logger LOG =
+            Logger.getLogger(GraylogDemoApplication.class);
+
+    public static void main(String[] args) {
+        SpringApplication.run(GraylogDemoApplication.class, args);
+        LOG.info("Hello from Spring Boot");
+    }
+}