Exclude specific dates to not run workflow on (ex. holidays/non-working days).

# Summary

Functionality to not run workflow(s) on certain dates. Like the holiday feature that SOS Berlin's jobscheduler has.

# Use Cases

For example when you or your company has fixed holidays/non-working days when you do not want certain workflow(s) to run.

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No files, tests, or entry points are named. Start by locating the workflow scheduling implementation and reviewing how scheduled runs are configured; done should define how workflows specify excluded holidays or non-working dates and verify that those runs are skipped.

Written by the indexing model from the issue text.