introduce CodeQL analysis

Author: gfx

.github/workflows/codeql.yml

@@ -0,0 +1,23 @@
+name: "CodeQL"
+
+on:
+  pull_request:
+  schedule:
+    - cron: '44 6 * * 6'
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        languages: typescript
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1