Add extra files to all tasks.

[dthain]

Per @hannahbnelson, add a top level feature to add extra input files to all tasks, or all tasks of a specific type, to enable passing in custom code that is not part of the Conda environment.

[btovar]

This should already be available with the extra_files argument to CoffeaDynamicDataReduction. It is a list of files/directories to be added to each task. @hannahbnelson, could you confirm?

[hannahbnelson]

@btovar That works! Before I was looking for that kind of option in the TaskVine manager and didn't realize I could do that through DDR itself. Thanks!