Implement BigInt.prototype[ @@toStringTag ]

[HalidOdat]

ECMASCript feature

Implement BigInt.prototype[ @@toStringTag ], as a reference on how to implement you can check #1225 (Math[ @@toStringTag ]).

Example code
This code should now work and give the expected result:

let result = BigInt.prototype[Symbol.toStringTag];

console.log(result);

The expected output is "BigInt".

[n14little]

I'll take this.