Add reusable GitHub Action for CI integration

[Pavithran-R-A]

Problem

Currently users must manually set up a workflow with actions/checkout, actions/setup-node, and npx setupsentry scan. A reusable composite action would simplify CI integration.

Proposed Scope

Create a composite GitHub Action that:

• Checks out the repository
• Sets up Node.js
• Runs SetupSentry scan
• Supports configurable failure threshold

Files/Components

• action.yml at repository root (composite action)
• README documentation with usage examples
• Test workflow that uses the action

Acceptance Criteria

• action.yml defines a usable composite action
• Action supports fail-on input parameter
• README documents action usage
• Example workflow shown in README is correct and tested
• All existing tests still pass