Fixes#57
This PR implements the 3-step plan proposed by @gr2m in
https://github.com/actions/create-github-app-token/issues/57#issuecomment-1751272252:
> 1. Support both input types
> 2. Log a deprecation warning for the old notation
> 3. Add a test for deprecations
Although this PR supports both input formats simultaneously, I opted
_not_ to document the old format in the updated README. That’s a
decision I’m happy to revisit, if y’all would prefer to have
documentation for both the old and new formats.
Clay Miller