Add option to create FileTime from custom date

[wldevries]

I'd like to have an option to create a FileTime struct for a specific date. Since FileTime can only be constructed from a SystemTime instance there is no way to initialize it with a specific date (unless I miss something).

API could look like that of chrono:

FileTime::ymd(2021, 11, 18).and_hms_milli(17, 00, 12, 123);