Show toast instead of throwing Error for maxFilesAtOnce
### What happened?

For some odd reason, decision was made to trigger `Error` instead of showing toast for `maxFilesAtOnce`. Can we turn this into toast so users can see it on UI, since all other checks do display toast...

```
editor.registerExternalContentHandler('files', async ({ point, files }) => {
    if (files.length > editor.options.maxFilesAtOnce) {
	    throw Error('Too many files')
    }
```
    

### How can we reproduce the bug?

_No response_

### What browsers are you seeing the problem on?

_No response_

### Where did this happen?

The developer package

### Contact Details

_No response_

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