drawCracks and createRubble (#6989)

core/src/mindustry/world/Block.java

@@ -166,6 +166,10 @@ public class Block extends UnlockableContent implements Senseable{
     public float baseExplosiveness = 0f;
     /** bullet that this block spawns when destroyed */
     public @Nullable BulletType destroyBullet = null;
+    /** whether cracks are drawn when this block is damaged */
+    public boolean drawCracks = true;
+    /** whether rubble is created when this block is destroyed */
+    public boolean createRubble = true;
     /** whether this block can be placed on edges of liquids. */
     public boolean floating = false;
     /** multiblock size */