Fixed type Inference with `custom` and `instanceof` in `catchall`

[taro-28]

Hello!

I noticed that when using custom or instanceof with catchall, the type inference using infer does not work. I have fixed it and added tests.

Before

const schema = z.object({ name: z.string() }).catchall(z.instanceof(Date));

// { name: string }
type Schema = z.infer<typeof schema>;

After

const schema = z.object({ name: z.string() }).catchall(z.instanceof(Date));

// { name: string } & { [k: string]: Date };
type Schema = z.infer<typeof schema>;