Add `createMany` IDs and MySQL warning

[WalkingPizza]

What does it do?

Documents https://github.com/strapi/strapi/pull/14269.

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Name	Status	Preview	Updated
documentation	✅ Ready (Inspect)	Visit Preview	Sep 7, 2022 at 9:36AM (UTC)

[pwizla]

Thanks for taking care of this, @WalkingPizza! 🤗 Looks good to me so far. Please let me know when it's ready for final review.

[pwizla]

Closing as it was handled by #1609 :)