[pt-br] Localize contribute/participate/_index.md

**This is a Feature Request**
The page "Participating in SIG Docs" does not currently exist in Brazilian Portuguese (PT-BR).

English page: https://kubernetes.io/docs/contribute/participate/
Page path in the repository: content/en/docs/contribute/participate/_index.md

**What would you like to be added**
Translate content/en/docs/contribute/participate/_index.md into Brazilian Portuguese (PT-BR).

**Why is this needed**
Because it broadens access to Kubernetes for those who don't speak English, strengthening the community and the adoption of the technology.

/language pt
/area localization
/sig docs
/assign