Add CodeQL (#774)

Add a workflow to run CodeQL against the codebase.

Author: martincostello

.github/workflows/code-scan.yml

@@ -0,0 +1,47 @@
+name: code-scan
+
+on:
+  push:
+    branches: [ dev* ]
+  pull_request:
+    branches: [ dev* ]
+  schedule:
+    - cron: "0 12 * * MON"
+  workflow_dispatch:
+
+permissions:
+  actions: read
+  contents: read
+
+jobs:
+  code-ql:
+
+    runs-on: ubuntu-latest
+
+    permissions:
+      security-events: write
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [ "csharp" ]
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v3
+
+    - name: Setup .NET SDK
+      uses: actions/setup-dotnet@v3
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v2
+      with:
+        languages: ${{ matrix.language }}
+
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@v2
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v2
+      with:
+        category: "/language:${{ matrix.language }}"