docs(oas/swagger): provide examples of the example and examples keys

[fbartkow-from-f]

Provide examples to users on how to set example and examples keys in the @ApiProperty annotation

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/nestjs/docs.nestjs.com/blob/master/CONTRIBUTING.md

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• Docs
• Other... Please describe:

What is the current behavior?

Currently the documentation does not have any indication of how to use the example or examples keys in the @ApiProperty(...) annotation.

Issue Number: N/A

What is the new behavior?

This PR adds an example for the example and an example for the examples keys to the documentation to help show how to use them.

Does this PR introduce a breaking change?

• Yes
• No

Other information

N/A - This is a pretty straightforward PR.

[kamilmysliwiec]

LGTM