add beforeDestroy to control the deletion of selected blocks

[AricZhu]

Sometimes we need to prevent the deletion of certain selected blocks, but the framework does not currently support this feature

Expected behavior:
Support preventing the deletion of certain selected blocks.

To do this, we can prevent deletions by adding the beforeSelectedDestroy hook function which return -1.

[korytovaf]

Have you solved this problem somehow? If I have a similar task, I need to prevent the deletion of a certain block and also prevent it from moving. I solved the deletion problem as follows - The block tool has the destroy method, which is called before deleting the block and in it I create a new duplicate of the deleted block and place it in the same place. But I can't find a similar method to move the block.