feat(outagedeck): add CLI feature

[koko3tallah]

What changed

• add an outagedeck Dev Container Feature that installs the OutageDeck CLI from GitHub Releases
• support both latest and pinned CLI versions
• document terminal and CI usage
• add default and pinned-version scenarios

Why

OutageDeck provides a small CLI for checking normalized status from official cloud and SaaS vendor feeds. Publishing it as a feature lets developers add the CLI to Codespaces and Dev Containers with one configuration entry.

Validation

• Dev Container CLI 0.88.0: test_default passed on Linux ARM64
• Dev Container CLI 0.88.0: test_specific_version passed for 0.1.0 on Linux ARM64
• latest installation resolved the correct outagedeck_0.1.0_linux_arm64.tar.gz release asset
• a live github provider query returned structured status during the installation smoke test
• the deterministic help assertion was separately exercised against the released CLI
• ShellCheck passed at error severity for both feature shell scripts
• JSON parsing, Bash syntax, and git diff --check passed

The project publishes both Linux AMD64 and ARM64 release archives; upstream CI will exercise the repository's native Linux runner.

Disclosure

I am contributing this on behalf of OutageDeck. The implementation and PR text were prepared with Codex/GPT-5 assistance and reviewed through the checks above.