Monster's damage vulnerabilities, resistances and immunities should be NamedAPIResource structures

Using full references makes the content better digestible by data-consuming applications, and also brings the structure of monsters' damage immunities/etc. in line with the structure of their condition immunities.

Instead of this:
```
damage_immunities: [
"acid"
]
```

We should see this:
```
damage_immunities: [
{
"index": "acid",
"name": "Acid",
"url": "/api/damage-types/acid"
}
]
```

Look at the monster data JSON files in the repository to see the current structure of damage_immunities, resistances, and vulnerabilities. Compare with the structure of condition_immunities which already uses NamedAPIResource. Update the relevant monster entries to use the new structure, ensuring the 'index', 'name', and 'url' fields are correctly populated from the damage-types API reference.

Escrita pelo modelo de indexação a partir do texto da issue.