Year expression

[hithaaaa]

• I'm submitting a ...
  [ ] bug report
  [ x ] feature request
  [ ] question about the decisions made in the repository
  [ ] question about how to use this project

• Summary
  This library doesn't have an expression for a given year/frequency of years. If I wanted a cron expression to also include a specific year to run or frequency to run, this is not generated or accounted for. This is important for when a cron expression validator expects 6 fields.

• Other information (e.g. detailed explanation, stack traces, related issues, suggestions how to fix, links for us to have context, eg. StackOverflow, personal fork, etc.)

• Modify data structure to include year enum and write functions similar to everyHour() or atHour().

[Victor1890]

Hi @hithaaaa, I think the best way to generate one year expression is to make combination to expression, for example: every year is "0 0 1 1 *".
Using expressions like this, you can make when you need it