added CodeQL workflow

Author: arturcic

.github/workflows/codeql-analysis.yml

@@ -0,0 +1,34 @@
+name: CodeQL
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+  schedule:
+    - cron: '41 21 * * 2'
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: [ 'csharp' ]
+ 
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        languages: ${{ matrix.language }}
+
+    - name: Autobuild
+      uses: github/codeql-action/autobuild@v1
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1