"Custom Block Types" doc doesn't work with drag and drop

[AgainstLightning]

Describe the bug
When moving the custom Alert element it does not work, the blocks vanish on move

To Reproduce

1. Visit https://www.blocknotejs.org/docs/custom-schemas/custom-blocks
2. Move the Alert element or any other lines

Misc

• Node version: N/A
• Package manager: N/A
• Browser: Brave
• I'm a sponsor and would appreciate if you could look into this sooner than later 💖

[nperez0111]

This example is a more fleshed out example of the full alert box integration: https://www.blocknotejs.org/examples/custom-schema/alert-block-full-ux

[YousefED]

@nperez0111 I think it's still a bug though, right? I think it's related to having multiple editors on the page, and a duplicate of #1653 that @matthewlipski is working on atm