reviewers not able to use the check command

[maelle]

https://github.com/ropensci/software-review/issues/633#issuecomment-2158854136

[mpadge]

Actual problem is that reviewers are listed without the prefixed "@", so not identified by GitHub handles, and therefore prohibited. Fix needs to ensure initial reviewer handles are pre-prended with "@".

[maelle]

or could the code add the @ if it's not there, so "just" making the code more robust?

[mpadge]

All okay; it was actually editors fault through issuing command assign person as reviewer rather than assign @person as reviewer.