Suggestion: bustools inspect for a filtered bus file

[NaotoKubota]

Hi, thank you for maintaining and improving this wonderful tool, you have helped my project a lot.
This is just a suggestion. It would be helpful if we could get inspect.json not only for unfiltered bus but also for filtered one, so that we can easily check a number of detected cells (barcodes) and other metrics like mean UMI per barcode that are important for QC.

Best