Add legacy ping support to PaperServerListPingEvent

Add a new method to StatusClient check if the client is a legacy
client that does not support all of the features provided in the
event.

paper-api/src/main/java/com/destroystokyo/paper/network/StatusClient.java

@@ -10,4 +10,16 @@ import com.destroystokyo.paper.event.server.PaperServerListPingEvent;
  */
 public interface StatusClient extends NetworkClient {
 
+    /**
+     * Returns whether the client is using an older version that doesn't
+     * support all the features in {@link PaperServerListPingEvent}.
+     *
+     * <p>For Vanilla, this returns {@code true} for all clients older than 1.7.</p>
+     *
+     * @return {@code true} if the client is using legacy ping
+     */
+    default boolean isLegacy() {
+        return false;
+    }
+
 }