Data freshness metric

**Is your feature request related to a problem? Please describe.**
I did not find Data freshness metric in the list of Analyzers. We would need this to verify we have the latest data

**Describe the solution you'd like**
An analyzer in deequ and pydeequ that can check data for staleness by days, hours, minutes

**Describe alternatives you've considered**
Considered using Python code to determine freshness but its probably more optimized in deequ (Scala)