ci: run codeql

.github/workflows/codeql.yml

+name: "CodeQL"
+
+on:
+  push:
+    branches: [ master, maint/* ]
+  pull_request:
+    branches: [ master, maint/* ]
+  schedule:
+    - cron: '21 3 * * 1'
+
+env:
+  docker-registry: docker.pkg.github.com
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Check out repository
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 0
+
+    # Initializes the CodeQL tools for scanning.
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        languages: 'cpp'
+
+    - name: Build
+      run: |
+        mkdir build
+        cd build
+        cmake .. -DREGEX_BACKEND=pcre -DDEPRECATE_HARD=ON -DUSE_BUNDLED_ZLIB=ON
+        cmake --build .        
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1