Only sync .serverless state if files exist, without having to comment out the step

You can get around the awkward "comment out this step for first run" if you use a bash if statement to check if files exist at that path or not before trying to sync from it:

```bash
if [[ $(aws s3 ls ${{ env.SERVERLESS_STATE_BUCKET_PATH }} | head) ]]; then aws s3 sync ${{ env.SERVERLESS_STATE_BUCKET_PATH }} .serverless --delete; fi
```