Typed or Copied Content Replaces Custom Alert Block Instead of Staying Within It

[lamtuanamc]

Description: I have customized a block type "alert" followed by a custom block on the BlockNote homepage. However, every time I type '-', '*', '+', '1.' or copy a text segment within the same editor, it replaces the "alert" block instead of placing the content within it.

Steps to Reproduce:

1. Create a custom "alert" block as per the documentation.
2. Type '-', '*', '+', '1.' or copy and paste a text segment within the "alert" block.
3. Observe that the content replaces the "alert" block instead of staying within it.

Expected Behavior: The typed or copied content should remain within the "alert" block instead of replacing it.

Actual Behavior: The "alert" block is replaced by the typed or copied content.

https://github.com/TypeCellOS/BlockNote/assets/37234239/b9ebe406-f2de-4b79-b3c7-d7b8d456ced9

Link to Documentation: BlockNote Custom Schemas - Custom Blocks