Thank you for your great project.

Subject of the issue

actionlint (and superlinter incorporating actionlint) will give an error for this action's sample that "pull-request-url is not defined".

Steps to reproduce

The result entered in actionlint is as follows.

https://rhysd.github.io/actionlint/#eJyNVMFu00AQvecrRhUoUpEdFW6rqkqFEBwAVRE9VTms7Ulsst41O7NJo5J/Z2ynYW1S4JCDZ9+8eTNvJt9dRmoCkHvUjHfBmAX+CEjcBgF8sJQ4qyBkwXJIjICIuydibKhHASQQCEmBzrlylmZ5ifnGBZ5v305OEKtrVPBFbxDyUts1ErCDRmqC74seoV1dBYUUgzevCW7kvXGeU37kMd37Tji0ymExYqkKBXnjT9+9xgYZfYJb3ersspNWQ3LUMN++OyXsKi7V6QtE7gZF2KunJyCUXKb07vYbHA4RJnd1XXFSI5Fei8D7puuj7+APnEhR8LHiTyGDa+sEZfbztZQNWSqImyhBBy6d76sfETJu56U8XJ8JzqVdT+mRND1PStXautVKwUobwugh89rmpQJ81HVjZESaxVSKEAUamWTyDGQf4nyu2Ej304cPPcFyOIhpXMoVewU/owi8OLXW+P6t6NyBS3aF3k/psluXEfI2sEvWaNF3CdkeHs44vny4Wk4GmRJQUDLLgs9mvwc3+8fqRBxGZ2ho3NWZdsRVV3fqokWVMLXO4GhfJzHVtsKdGPwSgFHXSYQaKnE7GQoNQrWuLMtvGK8rI505K15exeZ7veLnrRmfZHv8INffBKbhScciMC8dXMSHC19DnaEXou7C2j+YVO43PVKl8awT22MPh4u/c94vPv8fYfCmZfsFyPV/zw==