Support calendar years outside 0000..9999.
Astronomy Engine now supports times outside the years 0000..9999, and supports formatting those times as ISO 8601 text. Times within the year range 0000..9999 are still formatted like this:
2022-10-06T22:37:45.891Z
Based on ISO 8601, and following the convention Node.js uses, dates outside the range 0000..9999 are now formatted with a leading prefix of - or +, followed by a 6-digit integer like
-001234-12-25T14:37:57.450Z
+043752-10-30T09:30:18.256Z