Replace JohnnyGoodNews with jstammer in config.yaml

[JohnnyGoodNews]

Config changes proposed in this pull request

• switching the membership to my "business" github account (actual lastname but without cat profile pics 🥹)
• needed because I don't want to burn through company copilot tokens in hobby projects

For new organization members

I acknowledge that

• I have read and understood the Open Source Guidelines
• I agree to act accordingly (with due dilligence) to our guidelines
• I have no open questions regarding the topics covered (please delete the "open questions" section)

Open questions

• NOTE: would you be so kind to also invite the account jstammer instead for copilot usage? (left it with this account for reasons stated above)