docs(faq): document multiple global prefixes - #3531

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?

Issue Number: nestjs/nest#16095

The global prefix FAQ only shows a single string prefix. Regex prefixes like '(prefixOne|prefixTwo)' stopped working in v11, and the docs don't mention an alternative.

What is the new behavior?

Documents the array form of setGlobalPrefix() added in nestjs/nest#17713:

• app.setGlobalPrefix(['api', 'v1']) registers every route under each prefix, and a hint presents it as the replacement for regex prefixes.
• exclude works with multiple prefixes: excluded routes are served without any prefix.
• A warning that @nestjs/swagger only reads the first prefix, both in the generated document and for useGlobalPrefix.

Does this PR introduce a breaking change?

• Yes
• No

Other information

This is a draft until nestjs/nest#17713 is merged and released. After that, the page could say which version added array support.

How the content was checked:

• The documented behavior was confirmed with a temporary integration test against feat(core): add support for array of global prefixes nest#17713, on Express and Fastify: routes and middleware respond under each prefix, and excluded routes respond only without a prefix.
• The Swagger warning is based on lib/utils/get-global-prefix.ts in nestjs/swagger, which calls getGlobalPrefix() and so only gets the first prefix.
• npm run docs-only generated all 136 docs, with no unmatched-link warnings from this page.