add hologram line count to api

api/src/main/java/lol/pyr/znpcsplus/api/hologram/Hologram.java

@@ -6,4 +6,5 @@ public interface Hologram {
     void removeLine(int index);
     void clearLines();
     void insertLine(int index, String line);
+    int lineCount();
 }

plugin/src/main/java/lol/pyr/znpcsplus/hologram/HologramImpl.java

@@ -132,6 +132,11 @@ public class HologramImpl extends Viewable implements Hologram {
         }
     }
 
+    @Override
+    public int lineCount() {
+        return lines.size();
+    }
+
     @Override
     protected void UNSAFE_show(Player player) {
         for (HologramLine<?> line : lines) line.show(player);