`is.urlString` narrows the type

[risu729]

urlString narrows the type to string, which is correct, but it also narrows the type to non-string types in the else clause.
It is wrong type assertion as the value can be non-url strings.

Notice that TypeScript not only knows that pet is a Fish in the if branch; it also knows that in the else branch, you don’t have a Fish, so you must have a Bird.
https://www.typescriptlang.org/docs/handbook/2/narrowing.html#using-type-predicates

is/source/index.ts

Lines 755 to 766 in e097645

	export function isUrlString(value: unknown): value is string {
	if (!isString(value)) {
	return false;
	}
	try {
	new URL(value); // eslint-disable-line no-new
	return true;
	} catch {
	return false;
	}
	}

[risu729]

Related to #176, but I don't have any idea how to express URL in type.
I tried value is ${string}`` but it didn't work. (It seems it is treated just the same as value is string)