added missing javadoc

Author: jasonlessenich

src/main/java/net/javadiscord/javabot/data/h2db/message_cache/MessageCache.java

@@ -30,6 +30,9 @@
  */
 @Slf4j
 public class MessageCache {
+	/**
+	 * A memory-cache (list) of sent Messages, wrapped to a {@link CachedMessage} object.
+	 */
 	public List<CachedMessage> cache = new ArrayList<>();
 	/**
 	 * Amount of messages since the last synchronization.