"Dropdowns" in Markdown

dropdown.md

How do I dropdown?

This is how you dropdown.

<details>
<summary>How do I dropdown?</summary>
<br>
This is how you dropdown.
</details>

---

Want to ruin the surprise?

Well, you asked for it!

<details open>
<summary>Want to ruin the surprise?</summary>
<br>
Well, you asked for it!
</details>

Alerts outside of dropdown works fine

Important

Important note

But this does not work

[!IMPORTANT]
Another important note

https://docs.github.com/en/get-started/writing-on-github/getting-started-with-writing-and-formatting-on-github/basic-writing-and-formatting-syntax#alerts