Add README for business time utilities

Added README.md for business time utilities that provide functions for adding working hours, calculating working minutes, finding next open time, and checking schedule inclusion.

Author: hanna-g-sn

Core ServiceNow APIs/GlideDateTime/Business time utilities (add, diff, next open, in schedule)/README.md

@@ -0,0 +1,31 @@
+# Business time utilities (add, diff, next open, in schedule)
+
+## What this solves
+Teams repeatedly reimplement the same business-time maths. This utility wraps `GlideSchedule` with four practical helpers so you can:
+- Add N working hours to a start date
+- Calculate working minutes between two dates
+- Find the next open time inside a schedule
+- Check if a specific time is inside the schedule window
+
+All functions return simple objects that are easy to log, test, and consume in Flows or Rules.
+
+## Where to use
+- Script Include in global or scoped app
+- Call from Business Rules, Flow Actions, or Background Scripts
+
+## Functions
+- `addWorkingHours(scheduleSysId, hoursToAdd, startGdt, tz)`
+- `workingMinutesBetween(scheduleSysId, startGdt, endGdt, tz)`
+- `nextOpen(scheduleSysId, fromGdt, tz)`
+- `isInSchedule(scheduleSysId, whenGdt, tz)`
+
+## Notes
+- The schedule determines both business hours and holidays.
+- `tz` is optional; if omitted, the schedule’s TZ or instance default applies.
+- All inputs accept either `GlideDateTime` or ISO strings (UTC-safe).
+
+## References
+- GlideSchedule API  
+  https://www.servicenow.com/docs/bundle/zurich-api-reference/page/app-store/dev_portal/API_reference/GlideSchedule/concept/c_GlideScheduleAPI.html
+- GlideDateTime API  
+  https://www.servicenow.com/docs/bundle/zurich-api-reference/page/app-store/dev_portal/API_reference/GlideDateTime/concept/c_GlideDateTimeAPI.html