Can't pass null as 2nd parameter to stringify() #104

Describe the bug

I get this error when passing null as 2nd parameter to stringify():

TS2345 [ERROR]: Argument of type 'null' is not assignable to parameter of type '(string | number)[] | ((this: any, key: string, value: any) => any) | undefined'.
console.log(stringify({a:1, b:2}, null, 3));

I can pass null as 2nd parameter to JSON.stringify()
NOTE: I can, in fact, pass undefined as 2nd parameter to your stringify(), so I have an easy workaround

To Reproduce

console.log(stringify({a:1, b:2}, null, 3));

Platform/Env (please complete the following information):
$ deno --version
deno 2.9.3 (stable, release, x86_64-pc-windows-msvc)
v8 14.9.207.2-rusty
typescript 6.0.3

Using flatted 3.4.2

When I look at your stringify() function in github, it look like it should allow null, but it doesn't