Add run-script feature

[Copilot]

Adds a new run-script feature that executes a custom script during devcontainer build — either downloaded from a URL or provided as inline text.

Behavior

• url — downloads the script via wget (preferred) or curl; installs curl via apt if neither is present
• script — writes inline text to a mktemp temp file via printf | tee, then executes with bash
• Both provided → fails with an explicit error
• Neither provided → graceful no-op

Temp file is always cleaned up via trap.

Example usage

// devcontainer.json
{
  "features": {
    "ghcr.io/devcontainer-community/devcontainer-features/run-script:1": {
      "script": "apt-get install -y vim && echo 'done' > /tmp/setup-complete"
    }
  }
}

// or via URL
{
  "features": {
    "ghcr.io/devcontainer-community/devcontainer-features/run-script:1": {
      "url": "https://example.com/my-setup.sh"
    }
  }
}

Files

• src/run-script/devcontainer-feature.json — url and script string options (both default "")
• src/run-script/install.sh — install logic
• src/run-script/NOTES.md — feature documentation
• test/run-script/test.sh — autogenerated test (default empty options → no-op path)
• README.md — entry added alphabetically after ripgrep