Set packages author to "withastro"

[trueberryless]

Description

Recently I noticed that most packages in this mono-repo are authored under "Chris Swithinbank".
I know that he is the founder of Star(book)light, but at the same time I noticed that most other Astro repos either have no author or just "withastro". So I adapted it here as well.

If I am not aware that this project is still authored by Chris legally, then I am sorry for creating this PR.
Just let me know if I should adapt or close this PR!

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Latest commit: 2b33204

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