It could be handy to have some additional ICU version information available, besides just the icu version itself. since the ICU features have more and more applicability to various parts of Node.

These could go into process.versions, or not.
Note that for the CLDR and TimeZone version, we actually need to read data files to get the answer. So, I'd hesitate to just stuff constants into process.versions. Is there a way to lazily-initialize a constant?

Unicode Data Version

 unicode: '9.0'

This gives information about which Unicode Version is included. This would affect which characters are interpreted by regexes, etc.

Implementation: u_getUnicodeVersion() (doesn't actually read any data files to get the result)

CLDR Version

 cldr: "30.0.2"

This is the version of the CLDR data files used for ICU's implementation.

Time Zone Data Version

 tz: "2016g"

This is the version of the iana tz database.

cc: @nodejs/intl