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.

examples/check-on-pr.yml

@@ -0,0 +1,18 @@
+# Block infected merges. Add `scan` as a REQUIRED status check in your branch
+# protection / rulesets so a PR can't merge while malware is detected.
+name: PolinRider scan
+on: [pull_request]
+
+permissions:
+  contents: read
+  pull-requests: write # only needed for the PR comment; drop if comment-on-pr: false
+
+jobs:
+  scan:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: RMSoft-ltd/polinrider-cleanup@v1
+        with:
+          mode: check
+          # token defaults to ${{ github.token }} — only needed here for the PR comment