Add initial implementation of PolinRider malware scanner

- Introduced core files including Dockerfile, action.yml, and entry point script (bin/polinrider.js) for the PolinRider malware scanner.
- Created configuration files: .env.example, .gitignore, and .npmrc for environment setup and dependency management.
- Added CI workflows for testing, building, and releasing the action, along with examples for usage in GitHub Actions.
- Implemented a README.md to provide documentation on usage, features, and setup instructions.
- Included necessary scripts for building the action and handling security measures during execution.
- Established a structured directory for reports and workspace management within Docker.
- Ensured all files are set up for a secure and efficient scanning process of GitHub repositories for PolinRider malware.

.gitignore

@@ -0,0 +1,16 @@
+node_modules/
+
+# NOTE: dist/ is intentionally committed — it is the GitHub Action's runtime
+# entrypoint (dist/ci.mjs), built from src/ci.js. Do not ignore it.
+
+# Secrets — never commit. (.env.example is the committed template.)
+.env
+.env.local
+.env.*.local
+.env.production
+.env.development
+
+
+# Local clone workspace / reports
+/workspace/
+/reports/