GHIssueStateReason should add reopened

While going against a repository I am involved with, I recieved this message in the console:
````
org.kohsuke.github.internal.EnumUtils getEnumOrDefault
WARNING: Unknown value reopened for enum class org.kohsuke.github.GHIssueStateReason, defaulting to UNKNOWN
````
Would be best if it was added for proper recognition.