Allow specific cells to contain errors

I've got some notebooks that intentionally have errors in specific cells for teaching purposes.

It would be great if there was a way to mark these cells as "expected errors" and just render the error in the output instead of stopping the notebook build with an error.

We've got a custom patched version of `PlutoSliderServer` which allows for specifying a list of cell UUIDs that we expect to have errors in, and any that error that aren't in that list cause the build to fail. Doing something similar could work here too, but would like your feedback @rikhuijzer for other potential solutions?