Add retry possibility

[cbobach]

Thanks for a nice project/action 🙇

After we have automated the issue creation of some of our cyclic tasks we have seen multiple errors raising from this action contributed to race conditions in the underlying API.

I believe that the errors can be contributed to the fact that we are opening and labeling new issues automatic and thus starting multiple runs of this action at the same time.

The current trigger is:

on:
  issues:
    types:
      - opened
      - transferred
      - labeled

I've tried to rerun more of our failed actions and they do succeed on the rerun. Therefore I'm proposing adding a retry possibility to the action such that the action is more resilient to race conditions like these.

I see that the errors we are seeing have been opened as issues:

• "The priority you are attempting to set for this record is not unique" #89
• Workflow fails if issue is already added to project #389

I've created the PR with existing actions in mind and made the new input non required and default to 0 such that changes won't affect existing uses of this action in case you approve of this change.