[RFC]: add GitHub workflow which upon opening of a PR labels it as "Good First PR"

[Planeshifter]

This issue proposes adding a new GitHub actions workflow that, when a contributor opens a new PR, labels it with the "Good First PR" label in case the PR body references a "Good First Issue".

Time estimate with AI: 30min.
Time estimate without AI: 1h.

[Planeshifter]

PR-URL: stdlib-js/stdlib#5470

Loom videos:
https://www.loom.com/share/f8a4477c4c3b406bad6a7a7466bdbd20?sid=f23d2fb0-4bb6-41f1-8581-6be2acabaf60
https://www.loom.com/share/3499b10c4ec84f35bd716204614edd3f?sid=43ad5798-1dc7-4102-aa1e-9d112d9fbff6
https://www.loom.com/share/75b1558040bc49dc8e7b0e786698425d?sid=3fa2cc0e-401c-4c4d-8e87-69802e8ff4a9

Time to completion: 57min.

[Planeshifter]

This was painful due to me using advanced features of jq only once in a blue moon. Would have been much faster with AI assistance.