Resolver for stats of collection

[Jarsen136]

Requirement

• extends collectionEntitiesConnection resolver or provide a new resolver
• input:

{
    offset
    limit
    where
    orderBy
}

• output:

{
   volume:  xxx, // Total trading turnover
   highestSale: xxx, // Maximum selling price
   totalCount: xxx     // count of nfts in this colleciton
}

[roiLeo]

related with #33?

[Jarsen136]

related with #33?

They are a little bit related, though, in this issue, we focus on every single one collection stats in the list.

[alko89]

Think totalCount is already there -> nftCount?