Add CodeQL workflow for security scanning

Author: DavidBlaa

.github/workflows/codeql.yml

@@ -0,0 +1,7 @@
+on:
+  push:
+    branches: [ master, rc ]    # Replace 'main' with your default branch name
+  pull_request:
+    branches: [ master, rc ]    # Triggers on PRs targeting only default branch
+  schedule:
+    - cron: '0 0 * * 1'   # Optional: weekly scan on default branch