Add repository security tooling

.github/dependabot.yml

@@ -0,0 +1,11 @@
+version: 2
+updates:
+  - package-ecosystem: npm
+    directory: /
+    schedule:
+      interval: weekly
+    open-pull-requests-limit: 5
+    labels:
+      - dependencies
+    commit-message:
+      prefix: deps

.github/workflows/ci.yml

@@ -2,7 +2,7 @@ name: Parlyn CI
 
 on:
   push:
-    branches: [ master, main ]
+    branches: [ main ]
   pull_request:
 
 jobs:
@@ -20,9 +20,10 @@ jobs:
         uses: actions/setup-node@v4
         with:
           node-version: ${{ matrix.node-version }}
+          cache: npm
 
       - name: Install dependencies
-        run: npm install
+        run: npm ci
 
       - name: Structural and syntax checks
         run: npm run check

.github/workflows/codeql.yml

@@ -0,0 +1,30 @@
+name: CodeQL
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  schedule:
+    - cron: '17 3 * * 1'
+
+jobs:
+  analyze:
+    name: Analyze JavaScript
+    runs-on: ubuntu-latest
+    permissions:
+      security-events: write
+      packages: read
+      contents: read
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@v3
+        with:
+          languages: javascript-typescript
+
+      - name: Perform CodeQL analysis
+        uses: github/codeql-action/analyze@v3