SPIGOT-5778: Added World.getGameTime method

By: Jakub Zacek <dawon.cz@gmail.com>

paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -812,6 +812,11 @@ public class CraftWorld implements World {
         }
     }
 
+    @Override
+    public long getGameTime() {
+        return world.worldData.getTime();
+    }
+
     @Override
     public boolean createExplosion(double x, double y, double z, float power) {
         return createExplosion(x, y, z, power, false, true);