Update generating-a-json-web-token-jwt-for-a-github-app.md

[mark-mxwl]

Why:

Closes: #29925

What's being changed (if available, include any code snippets, screenshots, or gifs):

Provided a working bash script for generating a JWT signed with RS256, as proposed in the comments. The script contains all of the required claims, and has been tested locally with the following sample usage and output:

Usage:

./JWT5.sh 1234 BashPEM.pem

Output:

JWT: ewogICAgInR5cCI6IkpXVCIsCiAgICAiYWxnIjoiUlMyNTYiCn0.ewogICAgImlhdCI6MTcwMjI0MDIxNiwKICAgICJleHAiOjE3MDIyNDA4NzYsCiAgICAiaXNzIjoxMjM0Cn0.UnXejj2L8UOBtTkRIxqf7nqnQGRaMr-fx9GN7XIPo3yeLOYYNRNjCZDcQq0f9gqMwy1s1eZmBCFzDpdzlaTbxAGK865tSOX97KREx5XmC8pKBfYBYjWDCMQY2PBngSQtPU0ZN-OFi7CSS-Fec5GvejBZIfjAsCmC8XrKFSVyCEWEiFoIjfhGnsaZ-aQDBqsVgS42Sk0XPYF4Pm2EB0Yxt2rzsncgWRCGd9kj-EG5JbnJKm8DQtk5eHaLasJlHSDVVSSLc0-y_el02RxUkH2QiUsObZOftQAIzgFWrGvsM08mwvahPB6miaP_CiT5cDt3H1zuWTaDkzyUbqhMzZZialQqxuRkt8hNoZhdToKJp_mkNV1Qsss_pXWdCSDM0gvlWr7mU0bEiKczyWNR0f5jNZfZJbnknTfSttzcTcFbAXw2iWIxRNTRd_FqFVZYN3RXA9dAiq5l78ny5WLaWyLRyJjrIVioRY2F1pgxL1De4KlUn6NX1EbxzNNQjiGc7Yru

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Source	Preview	Production	What Changed
apps/creating-github-apps/authenticating-with-a-github-app/generating-a-json-web-token-jwt-for-a-github-app.md	fpt ghec ghes@ 3.11 3.10 3.9 3.8 3.7 ghae	fpt ghec ghes@ 3.11 3.10 3.9 3.8 3.7 ghae

---

fpt: Free, Pro, Team
ghec: GitHub Enterprise Cloud
ghes: GitHub Enterprise Server
ghae: GitHub AE

[nguyenalex836]

@mark-mxwl Thanks so much for opening a PR! I'll get this triaged for review ✨

[mark-mxwl]

Thx @nguyenalex836!

[skedwards88]

Thanks for adding this example! I left some very minor suggestions that I will go ahead and incorporate, then we'll get this merged for you.

[mark-mxwl]

Amazing, thx so much @skedwards88!! This was a fun one 🙌

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