New feature to check for latest packages

[rasbt]

It would be nice to have a --check_latest flag that checks if the latest packages are installed. For example

%watermark --packages numpy
numpy: 1.22.1 (version 1.22.4 is available)

This could be build based on the dependency checker package's is_latest_version feature (https://github.com/muellerzr/dependency_checker)