Full support for ERC1155 on search endpoint

You can now search for ERC1155 collections and NFTs using our search endpoint.

We also added:

1. A new response field, contractType, that indicates the contract type for the collection (ERC1155 vs. ERC721)
2. A new query parameter, contractType, that lets you filter for specific contract types before you search

Check it out here: https://docs.center.dev/reference/search-v2