all_observer 1.3.2

Documentation/example-only release — no code changes to lib/, no breaking changes, no new external dependencies.

Added real, runnable tests under example/test/ proving the library's testability: a widget test, a pure-Dart controller unit test, a measurable rebuild-granularity test, a debounce worker test using flutter_test's virtual time, a deterministic ObservableFuture test via injected fakes, and a strictMode misuse test.
Extracted the example demos' business logic into constructor-injectable controllers under example/lib/controllers/ (CounterController, FruitSearchController, FetchController) — the "testable architecture" pattern the new guide recommends.
New documentation/en/testing.md / documentation/pt-BR/testing.md guide, linking every snippet to the real test file it comes from; linked from both READMEs, both FAQs, and the doc navigation chain.
Added example/README.md and wired example/ into CI (flutter test now also runs there).