add codeql workflow & dependabot for actions

.github/dependabot.yml

@@ -0,0 +1,7 @@
+version: 2
+
+updates:
+  - package-ecosystem: github-actions
+    directory: "/"
+    schedule:
+      interval: "daily"

.github/workflows/codeql.yml

@@ -0,0 +1,43 @@
+name: CodeQL
+
+env:
+  CODEQL_EXTRACTOR_CPP_AUTOINSTALL_DEPENDENCIES: false
+
+on:
+  push:
+    branches:
+    - main
+  pull_request:
+    branches:
+    - main
+  schedule:
+    - cron: 0 8 * * 1
+  workflow_dispatch:
+
+jobs:
+  analyze:
+    name: Analyze
+    runs-on: ubuntu-22.04
+    timeout-minutes: 10
+    permissions:
+      actions: read
+      contents: read
+      packages: read
+      security-events: write
+    strategy:
+      fail-fast: false
+    steps:
+    - uses: actions/checkout@v4
+    - name: Initialize CodeQL
+      uses: github/codeql-action/init@v3
+      with:
+        languages: c-cpp
+        build-mode: manual
+    - name: Install packages
+      run: sudo apt-get install gcc-multilib g++-multilib
+    - name: Build Linux (GCC)
+      run: gcc -std=c11 -m32 -shared -fPIC -Ofast -s -DNDEBUG prof.c -pthread -o libprof.so
+    - name: Perform CodeQL Analysis
+      uses: github/codeql-action/analyze@v3
+      with:
+        category: "/language:${{matrix.language}}"