chore(examples): add local file input example

[dkundel-openai]

We didn't have a good example of using local file inputs which caused confusion in #87 since the Responses API does not give a detailed error message if the filename property is missing

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[seratch]

For the purpose to add this example, the name local-file.ts is fine, but as we already have local-image.ts in the same directory, we may want to name this local-pdf.ts? Either is fine tho!

[dkundel-openai]

I think since the input type is file local-file makes more sense imo