Enhance Nfts loading

[GabrielePicco]

Enhance Nfts loading

Status	Type	⚠️ Core Change	Issue
Ready	Feature	No	#99

Problem

Users may need to load nfts metadata without the textures, e.g.: for gating the access to a content based on nfts ownership.

Solution

This can now be done with:

var nfts = await Web3.LoadNFTs(loadTexture: false);

Textures can be loaded afterward, e.g. for the first Nft:

await nfts[0].LoadTexture();

Others

• Fix a minor issue in Web3Auth

Issues

Closes #99