Initialize GitHub code scanning workflow using security-and-quality suite.

.github/codeql-config.yaml

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+name: "CodeQL Config"
+
+queries:
+  - uses: security-and-quality
+
+paths-ignore:
+  - demo/markdownlint-browser.js

.github/workflows/codeql-analysis.yml

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+name: "CodeQL"
+
+on:
+  pull_request:
+  push:
+  schedule:
+    - cron: '30 12 * * *'
+  workflow_dispatch:
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        language: ['javascript']
+
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+      with:
+        fetch-depth: 2
+
+    - run: git checkout HEAD^2
+      if: ${{ github.event_name == 'pull_request' }}
+
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v1
+      with:
+        config-file: ./.github/codeql-config.yaml
+        languages: ${{ matrix.language }}
+
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v1