docs(pt): translate handbook-v2/Type Declarations

[guuszz]

Summary

Adds the Brazilian Portuguese translation of Type Declarations from the TypeScript v2 Handbook, into docs/documentation/pt/handbook-v2/.

This continues the handbook-v2 PT-BR effort (#247–#253). Type Declarations covers what .d.ts files are, built-in type definitions, the target/lib settings, and external definitions (bundled types, DefinitelyTyped / @types, writing your own).

Translation choices

• Followed the established pt/ frontmatter convention: translated title and oneline, adapted permalink to /pt/docs/handbook/2/type-declarations.html.
• Preserved all code samples verbatim — the // @errors: 2339 directive, the npm install --save-dev @types/react command and the declare module example.
• Kept technical terms with a PT gloss on first use (e.g. arquivos de declaração (declaration files)).

Source

microsoft/TypeScript-Website @ packages/documentation/copy/en/handbook-v2/Type Declarations.md

Testing

Read side-by-side with the EN source; code fences (6) and the @errors code match. Cross-checked terminology against the already-merged pt/ pages and my sibling PRs (#247–#253).