Add scaladoc to codec annotations

[googley42]

Issue https://github.com/zio/zio-schema/issues/203 has been implemented but it looks like there are missing scaladoc for the annotations:

... add and document these annotations inside zio.schema.annotation ...

[jdegoes]

/bounty $100

[algora-pbc[bot]]

💎 $100 bounty created by ZIO 🙋 If you start working on this, comment /attempt #478 to notify everyone 👉 To claim this bounty, submit a pull request that includes the text /claim #478 somewhere in its body 📝 Before proceeding, please make sure you can receive payouts in your country 💵 Payment arrives in your account 2-5 days after the bounty is rewarded 💯 You keep 100% of the bounty award 🙏 Thank you for contributing to zio/zio-schema!

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Attempt	Started (GMT+0)	Solution
🟢 @iamorozov		#550

[iamorozov]

I would like to try this one

[algora-pbc[bot]]

💡 iamorozov submitted a pull request that claims the bounty. You can visit your org dashboard to reward. 👉 @iamorozov: To receive payouts, sign up on Algora, link your Github account and connect with Stripe on your dashboard.

[algora-pbc[bot]]

🎉🎈 @iamorozov has been awarded $100! 🎈🎊

[987Nabil]

@jdegoes @vigoo actually, for Scala 3 we can extract Scala doc at macro execution. But this ticket is now already rewarded and has a merged pr. Should we open a new issue?

[vigoo]

If we can capture it it would definitely be a nice feature