Add GitHub Actions security scanning with CodeQL and zizmor

.github/dependabot.yml

@@ -0,0 +1,15 @@
+version: 2
+updates:
+  - package-ecosystem: "github-actions"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    cooldown:
+      default-days: 7
+
+  - package-ecosystem: "mix"
+    directory: "/"
+    schedule:
+      interval: "weekly"
+    cooldown:
+      default-days: 7

.github/workflows/codeql.yml

@@ -0,0 +1,52 @@
+name: "CodeQL Advanced"
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+  schedule:
+    - cron: "29 8 * * 1"
+
+permissions:
+  contents: read
+
+jobs:
+  analyze:
+    name: Analyze (${{ matrix.language }})
+    runs-on: "ubuntu-latest"
+    permissions:
+      security-events: write
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - language: actions
+            build-mode: none
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - name: Initialize CodeQL
+        uses: github/codeql-action/init@89a39a4e59826350b863aa6b6252a07ad50cf83e # v4.32.4
+        with:
+          languages: ${{ matrix.language }}
+          build-mode: ${{ matrix.build-mode }}
+      - name: Perform CodeQL Analysis
+        uses: github/codeql-action/analyze@89a39a4e59826350b863aa6b6252a07ad50cf83e # v4.32.4
+        with:
+          category: "/language:${{matrix.language}}"
+
+  zizmor:
+    name: Zizmor
+    runs-on: ubuntu-latest
+    permissions:
+      security-events: write
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+        with:
+          persist-credentials: false
+      - name: Run zizmor
+        uses: zizmorcore/zizmor-action@0dce2577a4760a2749d8cfb7a84b7d5585ebcb7d # v0.5.0

.github/workflows/main.yml

@@ -2,6 +2,9 @@ name: CI
 
 on: [push, pull_request]
 
+permissions:
+  contents: read
+
 jobs:
   test:
     name: Test
@@ -31,10 +34,12 @@ jobs:
           - erlang: "19.3.6"
             elixir: "1.5.3"
     steps:
-      - uses: actions/checkout@v1
+      - uses: actions/checkout@50fbc622fc4ef5163becd7fab6573eac35f8462e # v1.2.0
+        with:
+          persist-credentials: false
 
       - name: Install OTP and Elixir
-        uses: erlef/setup-elixir@v1
+        uses: erlef/setup-elixir@ee09b1e59bb240681c382eb1f0abc6a04af72764 # v1.23.0
         with:
           otp-version: ${{matrix.erlang}}
           elixir-version: ${{matrix.elixir}}