write subscriptions for the block and transactions table

[skunal8197]

test with @DenisIvanov26

[skunal8197]

relevant code

subscribeToMore({
      document: SUBSCRIBE_BLOCK_CHANGES,
      variables: { fetchPolicy: "cache-and-network", num: limit, offset: (currentPage - 1) * limit },
      updateQuery: (prev, { newData }) => {
        if (!newData) return prev;
        const newBlock = newData.blocks[0]
        return Object.assign({}, prev, {
          blocks: [newBlock, ...prev.blocks]
        });
      }
    })