ci: enable CodeQL code scanning (#5279)

Co-authored-by: Dean Sheather <dean@deansheather.com>
Co-authored-by: Mathias Fredriksson <mafredri@gmail.com>
Co-authored-by: Geoffrey Huntley <ghuntley@ghuntley.com>

.vscode/extensions.json

@@ -1,5 +1,6 @@
 {
   "recommendations": [
+    "github.vscode-codeql",
     "golang.go",
     "hashicorp.terraform",
     "esbenp.prettier-vscode",