[TypeScript] object properties or class fields, methods are also converted to snake_case

[yutak23]

I use this library in TypeScript (thank you for developing it).

I have recently submitted an issue, but I have found another issue, so I would like to report it again.

When the following implementation, the type definitions of Date and class fields and methods are also converted to snake_case.

class Point {
	x: number;
	y: number;
	addPoint(point: Point): Point {
		return ...;
	}
	constructor(x: number, y: number) {
		...
	}
}

interface Person {
	firstName: string;
	lastName: string;
	age: number;
}

const point = new Point(0, 10);
const person: Person = {
	firstName: 'Yuta',
	lastName: 'Katayama',
	age: 30
};

const result1 = snakecaseKeys({ foo: person, nested: { fooBaz: point } });
const result2 = snakecaseKeys({ fooBaz: "fooBaz", foo_bar: new Date() });

// type structure of `result1`
const result1: {
    foo: {
        first_name: string;
        last_name: string;
        age: number;
    };
    nested: {
        foo_baz: {
            x: number;
            y: number;
            add_point: {};
        };
    };
}

// type structure of `result2`
const result2: {
    foo_baz: string;
    foo_bar: {
        to_string: {};
        to_date_string: {};
        to_time_string: {};
        to_locale_string: {};
        to_locale_date_string: {};
        to_locale_time_string: {};
        value_of: {};
        get_time: {};
        get_full_year: {};
        ... 34 more ...;
        [Symbol.toPrimitive]: {};
    };
}