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.

scripts/build-action.mjs

@@ -0,0 +1,31 @@
+/**
+ * Bundle the GitHub Action entrypoint (src/ci.js) into a single self-contained
+ * dist/ci.mjs that the action runner executes with no install step.
+ *
+ * The banner shims `require`/`__dirname`/`__filename` because some transitive
+ * CJS deps of execa (e.g. cross-spawn) call `require('child_process')`, which
+ * does not exist in an ESM bundle without this.
+ */
+import { build } from "esbuild";
+
+const banner = [
+  "import { createRequire as __createRequire } from 'node:module';",
+  "import { fileURLToPath as __fileURLToPath } from 'node:url';",
+  "import { dirname as __pathDirname } from 'node:path';",
+  "const require = __createRequire(import.meta.url);",
+  "const __filename = __fileURLToPath(import.meta.url);",
+  "const __dirname = __pathDirname(__filename);",
+].join("\n");
+
+await build({
+  entryPoints: ["src/ci.js"],
+  bundle: true,
+  platform: "node",
+  format: "esm",
+  target: "node20",
+  outfile: "dist/ci.mjs",
+  banner: { js: banner },
+  legalComments: "none",
+});
+
+console.log("built dist/ci.mjs");