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

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+# 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

examples/fix-on-push.yml

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+# Auto-clean pushes to the default branch and commit the fix back.
+# commit-back works on push events (not pull_request — see README). Pushes made
+# with the default GITHUB_TOKEN do NOT retrigger workflows, so there's no loop.
+name: PolinRider auto-clean
+on:
+  push:
+    branches: [main]
+
+permissions:
+  contents: write # required to commit the cleanup back
+
+jobs:
+  clean:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: RMSoft-ltd/polinrider-cleanup@v1
+        with:
+          mode: fix
+          commit: true
+          token: ${{ secrets.GITHUB_TOKEN }}

examples/pr-scheduled.yml

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+# Scan the default branch on a schedule and open a cleanup PR if anything is
+# found. Good for fork PRs / protected branches where commit-back can't push.
+name: PolinRider weekly scan
+on:
+  schedule:
+    - cron: "0 6 * * 1" # Mondays 06:00 UTC
+  workflow_dispatch:
+
+permissions:
+  contents: write # create the cleanup branch
+  pull-requests: write # open the PR
+
+jobs:
+  scan:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: RMSoft-ltd/polinrider-cleanup@v1
+        with:
+          mode: pr
+          token: ${{ secrets.GITHUB_TOKEN }}
+          # auto-merge: true        # respects branch protection
+          # merge-method: squash