[pt] Add pt/content/docs/concepts/observability-primer.md

[EzzioMoreira]

Add a localization to the observability-primer.md.

Issue: #4922

[svrnm]

pt/docs/index.html
  hash does not exist --- pt/docs/index.html --> concepts/observability-primer/#what-is-observability
pt/docs/concepts/observability-primer/index.html
  hash does not exist --- pt/docs/concepts/observability-primer/index.html --> #distributed-traces
  hash does not exist --- pt/docs/concepts/observability-primer/index.html --> #spans
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there are a few more hashes that require some of that treatment :)

[lgfa29]

Não sei o que aconteceu, mas esses valores acabaram mudando em comparação com #4946

[chalin]

All checks are green, and @svrnm's concerns have been addressed (and is OOO), so I'm approving and merging on behalf of @open-telemetry/docs-maintainers & @svrnm.