Add Flawfinder workflow for security scanning (#4979)

Signed-off-by: Niels Lohmann <mail@nlohmann.me>

.github/workflows/flawfinder.yml

@@ -0,0 +1,38 @@
+# This workflow uses actions that are not certified by GitHub.
+# They are provided by a third-party and are governed by
+# separate terms of service, privacy policy, and support
+# documentation.
+
+name: flawfinder
+
+on:
+  push:
+    branches: [ "develop" ]
+  pull_request:
+    # The branches below must be a subset of the branches above
+    branches: [ "develop" ]
+  schedule:
+    - cron: '41 14 * * 3'
+
+jobs:
+  flawfinder:
+    name: Flawfinder
+    runs-on: ubuntu-latest
+    permissions:
+      actions: read
+      contents: read
+      security-events: write
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: flawfinder_scan
+        uses: david-a-wheeler/flawfinder@8e4a779ad59dbfaee5da586aa9210853b701959c
+        with:
+          arguments: '--sarif ./'
+          output: 'flawfinder_results.sarif'
+
+      - name: Upload analysis results to GitHub Security tab
+        uses: github/codeql-action/upload-sarif@v3
+        with:
+          sarif_file: ${{github.workspace}}/flawfinder_results.sarif