Add GitHub Actions workflow to build and release whisper-stream binaries

[newbeelearn]

Motivation

• Provide a reproducible GitHub Actions workflow to build whisper-stream on macOS and Linux and publish prebuilt binaries as a release.
• Automate dependency installation, cmake configuration, and packaging to reduce manual release steps.
• Support creating releases via workflow_dispatch with a tag and optional prerelease flag.

Description

• Adds .github/workflows/stream-release.yml which triggers on workflow_dispatch and accepts tag and prerelease inputs.
• Builds whisper-stream in a matrix for ubuntu-latest and macos-latest, installing platform dependencies (libsdl2/sdl2) and running cmake to configure and build the whisper-stream target.
• Collects the compiled binary into dist/whisper-stream-<os>-<arch>, uploads per-platform artifacts with actions/upload-artifact@v4, and then assembles and publishes a GitHub release using softprops/action-gh-release@v2 with the provided tag and prerelease setting.

Testing

• No automated tests were executed as part of this change; the new workflow file was added to the repository and will execute when manually dispatched.

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Codex Task