feat(swagger) add TOML document endpoint support

[camargo-leonardo]

PR Checklist

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• The commit message follows our guidelines: https://github.com/nestjs/nest/blob/master/CONTRIBUTING.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

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
• CI related changes
• Other... Please describe:

What is the current behavior?

Issue Number: 3743

What is the new behavior?

The Swagger module now supports serving the OpenAPI document in TOML format (via ‎{{path}}-toml or a custom ‎tomlDocumentUrl), controlled by the ‎raw option, including when using a global prefix and ‎patchDocumentOnRequest.

Does this PR introduce a breaking change?

• Yes
• No

Other information

[kamilmysliwiec]

I'd say we shouldn't be adding more packages to this repository. If one wants to serve TOML, it seems that it should be quite simple to implement themselves (no need for changes in this repo)