`:::keys` for `.md` doesn't work

### Describe the bug Let's see e.g: https://github.com/wxt-dev/wxt/blob/main/docs/guide/introduction.md As you can see `:::warning` doesn't work. We should change it to `[!WARNING]`: https://github.com/orgs/community/discussions/16925#discussion-4085374 Let's see for other `:::keys` in all `.md` files and change it.