Fix VNDA and Nuvemshop sellers

## Issue Type

Please select the type of issue you are reporting:

- Feature Request

## Description

The functions that generate Offers should return the responsible seller. Currently, in the Nuvemshop, Vnda, and Linx-Impulse integrations, this is being populated with the platform's own name. We need to identify how to retrieve the actual seller.

## Steps to Reproduce (for bugs)

Go to function:
```
const offers: Offer[] = [{
"@type": "Offer" as const,
seller: "VNDA", // PROBLEM HERE
price,
priceSpecification,
inventoryLevel: {
value: available_quantity,
},
availability: available
? "https://schema.org/InStock"
: "https://schema.org/OutOfStock",
}];
```

## Expected Behavior

Correct seller as we have in VTEX Integration:

```
const toOffer = (
{ commertialOffer: offer, sellerId, sellerName }: SellerVTEX,
): Offer => ({
"@type": "Offer",
price: offer.spotPrice ?? offer.Price,
seller: sellerId, // CORRECT DYNAMIC VALUE
```