Should VestingScheduleRelativeTrigger Support Years-Based Vesting Periods?

[JSv4]

The period field of VestingScheduleRelativeTrigger only supports months and days as time periods. Since we also have years defined elsewhere, I think it would make sense to create a VestingPeriodInYears type, just as we have a VestingPeriodInDays and VestingPeriodInMonths. Understood that it's certainly possible to get away without it, but seems like it would be more natural to have the option.

[pjohnmeyer]

We deliberately chose not to support years because "ideal" years can be expressed in days, and calendar years can be expressed in months. We should add a note to the documentation to make it clearer.