fix(astro): fix types, zod validation (#5052)

Previously, in the types, `options` were optional, but they are required.

Zod validation additionally marked the *entire* options objects as optional. But it is instead *fields* that are (sometimes) optional.

To make sure the types are correct, I used `satisfies IntegrationRule<>`. To make sure Zod is correct, you can use something like:

```ts
const example: z.infer<typeof validateSlidingWindowOptions> = {
  interval: 123,
  max: 123,
};
```

I verified with the Astro example, and noticed that it said every email I provided was invalid. That led me to think something was wrong. So instead of denying most emails with an empty `allow: []`, this now allows free emails (such as gmail) and emails w/o gravatar (such as my work email).

Closes GH-5016.

Author: wooorm-arcjet