nullable inputs/args are not covered in the docs very well

Firstly, this feels a bit stupid to be noticing after using type-graphql for 2 years but here it goes...

Describe the issue

The docs seemingly made it clear to me that having nullable was equivalent to an optional type... e.g.

@Field({ nullable: true })
averageRating?: number;

and/or

@InputType()
export class RecipeInput {
  @Field()
  title: string;

  @Field({ nullable: true })
  description?: string;
}

and this is mostly true for fields but it comes to args/inputs its misleading ... as I've just found out while debugging an issue in my project.

The correct typescript types for this should be

@Field({ nullable: true })
averageRating?: number | null;

and/or

@InputType()
export class RecipeInput {
  @Field()
  title: string;

  @Field({ nullable: true })
  description?: string | null;
}

I haven't seen this mentioned in the docs (and it feels like I'm stating the obvious) but when using nullable, null is a valid input for args/fields/etc and I've just realized a bunch of code with optional chaining is very broken now

Are you able to make a PR that fix this?

Would be good to get it confirmed that I'm not crazy in noticing this and it's not already mentioned somewhere I haven't seen... its a bit late where I am and I've also been chasing this issue all afternoon only to realize this now...

Additional context

Specifically, I've been working on Query with the following signature...

@Query(() => SomeResponse)
async allThings(
  @Arg('filter', { nullable: true }) filter?: SomeFilter,
): Promise<Response<ISomething>> {
  // ...

  console.log(filter?.search); // undefined or SomeFilter right?
}

and just realized this is a very valid GQL query for it:

{
  allThings(filter: null) {
    id
  }
}

and with this, console.log(filter?.search) will now error because "Cannot read properties of null (reading 'search')"