Maybe add years

For very large durations

_maybe_ document 365 fixed days but there is a risk people try to add said duration in bissextile year and be surprised so it depends on context

months we should definitely not add weeks is enough and unambiguous

No file or test is named. Review the duration input and output behavior described by the repository, then determine whether years should be supported and whether they mean 365 fixed days or calendar-aware durations; done means the semantics are decided and documented.

Written by the indexing model from the issue text.