Add Codex plugin scanner workflow

Author: Taisly

.github/workflows/plugin-security-scan.yml

@@ -0,0 +1,20 @@
+name: Plugin Security Scan
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+permissions:
+  contents: read
+
+jobs:
+  scan:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: hashgraph-online/ai-plugin-scanner-action@v1
+        with:
+          plugin_dir: "."
+          fail_on_severity: high