Support multiple collections on collections filter

[dandlezzz]

Add support for multiple collections like so:

nfts(
      owners: ["4N98VatE2kMPEokHpz6DNs9vnFNAaeXv4VpxzK62fhVS"], 
      collections:["F33hSfqB7gDHhKmSpYMq9fqgnpqxGEXY6En4vvMeAJnd", "2nd collection address"],
      limit:999,
      offset: 0) {
        name
    }