Use correct moving tag in readme examples

[hazelweakly]

When I first wrote the README examples, I used v1.1 because I assumed it would also be a moving tag, and it was using some features that only came out in the rewrite. However, only the v1 tag is being updated (which seems to be a common practice across all of the setup-x actions).

This fixes the README to use a tag that actually updates so that people don't need to churn through point releases.

Fixes #51

[thboop]

Thanks for taking care of this @jared-w 😄