Update credits

[czyzby]

Add missing entry to the about.cfg file. See #6475.

[stevecotton]

My apologies for asking you to create this PR before I asked @doofus-01 about whether the credit should go in the Artists or Miscellaneous Contributors section.

@doofus-01, please would you say which section this should be in?

[czyzby]

@stevecotton I didn't realize that sprite changes can be credited in a different section. Feel free to close the PR if you'd prefer to update the credits in bulk once the details are established.

[doofus-01]

The credits are a mess, I don't think the section matters much at this point. More important is to get the "comment" key to be an accurate description, and that part looks OK to me.