[C++]Sync the sample monster.fbs file with the tutorial (#5277)

* Fix the header file path in the tutorial doc

* Add the path field in sample/monster.fbs to match the tutorial

* Update the lobster sample file

* Update the binary sample file

samples/monster.fbs

@@ -22,6 +22,7 @@ table Monster {
   color:Color = Blue;
   weapons:[Weapon];
   equipped:Equipment;
+  path:[Vec3];
 }
 
 table Weapon {