v2.0.0

This PR upgrades the actions version as a breaking change from v1.0.0 has been released.

Rather than using ${{ github.event.issue.number }} as a default for the issue-number input, the following value will be used: ${{ github.event.number }}

This value is more likely to work "out of the box" for more Actions contexts and workflows which will prevent users from having to determine their contexts and set that variable explicitly.