feature request: to add null values count to stats

[aborruso]

stats is really great, to have null values count should be very interesting.

As usual thank you for this great tool

[jqnatividad]

@aborruso , you may want to check out qsv - a fork of xsv.

It has nullcount, infers Date/DateTime data types, along with some additional descriptive statistics for stats.

[aborruso]

@jqnatividad thank you very much