bump pion/stun to v3 to fix vulnerability (#5245)

.github/workflows/security.yml

@@ -0,0 +1,21 @@
+name: Security Scan
+
+on:
+  schedule:
+  - cron: "0 13 * * 1"
+  push:
+    branches:
+    - master
+    - dev
+  pull_request:
+    branches:
+    - master
+    - dev
+
+jobs:
+  vulncheck:
+    name: Scan for vulnerabilities in Go code
+    runs-on: ubuntu-latest
+    steps:
+    - name: govulncheck
+      uses: golang/govulncheck-action@v1