chore(blob-explorers): accomodate new blobscan API changes (#68)

Blobscan had some more API changes. They added a few things:
- a field for tx category, present on both block/tx responses.
- added the rollup field for the block response as well.
- They renamed the `DataStorageReferences` fields to be `storage` and
`url`.

This aligns the new responses to the new format, and another tx test.
[See their API
docs](https://api.blobscan.com/#/blocks/block-getByBlockId). Although I
saw #66 open, the
behavior implemented in that PR doesn't seem up to date anymore.

Author: Evalir