docs: explain default error handler behaviour

[ST-DDT]

Description of Problem

Currently, it is very hard to understand how the default error handler behaves.

• It throws during development, triggering the global error handler.
• It only logs/does not throw in production, causing error events missing in the error reporting loop.
• The difference in behavior causes confusion

Proposed Solution

Explicitly mention the default behaviour and link to properties to configure this. Feel free to suggest improvements or different solutions.

Preview: https://deploy-preview-3320--vuejs.netlify.app/api/application.html#app-config-errorhandler

Additional Information

I spend multiple hours trying to detect why no errors were reported to our monitoring solution. In the end, I had to look into the default error handler source code to become aware of the throwunhandlederrorinproduction property. During my search I didn't find any other part in the documentation mentioning this behavior, the errorhandler and throwunhandlederrorinproduction properties being separated by a bunch of other properties didn't help either.

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