[Sync EN] Add documentation for 6 new pcntl functions (PHP 8.4) (#5350)

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Commit: https://github.com/php/doc-en/commit/acb474ea92ab6226eaf419a85de05f68c6715a9f
PR: https://github.com/php/doc-en/pull/5350

Nuevos archivos EN (aún no traducidos)

• reference/pcntl/functions/pcntl-forkx.xml
• reference/pcntl/functions/pcntl-getcpu.xml
• reference/pcntl/functions/pcntl-getqos-class.xml
• reference/pcntl/functions/pcntl-setns.xml
• reference/pcntl/functions/pcntl-setqos-class.xml
• reference/pcntl/functions/pcntl-wifcontinued.xml