exclude-file and EventGrid examples

Looking at [the avocado check failure](https://github.com/Azure/azure-rest-api-specs/pull/24015) I can't make it skip the examples.

The reason the examples can't be linked to anything in the spec is because the samples are required to include the event envelope, while the spec only defines payload in the `data` attribute.

Uncommenting `exclude-file` in the readme.md doesn't seem to do anything, I tried multiple ways to specify the path.

Please advise.

Start with readme.md and the exclude-file option, then reproduce the avocado check failure described for PR #24015 using the EventGrid examples. Trace how the configured path is applied; done means exclude-file reliably skips the intended examples while leaving other validation behavior unchanged.

Written by the indexing model from the issue text.