Add Dialyzer CI job

.github/workflows/quality.yml

@@ -42,3 +42,36 @@ jobs:
 
       - name: Run credo
         run: mix credo
+  dialyzer:
+    name: Dialyzer
+    runs-on: ubuntu-24.04
+
+    strategy:
+      fail-fast: false
+
+    steps:
+      - name: Set up Elixir and OTP
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.elixir_version }}
+          otp-version: ${{ env.otp_version }}
+
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: 'Restore cache for deps/ and _build/ directories'
+        uses: actions/cache@v4
+        with:
+          path: |
+            deps
+            _build
+          # Dialyzer uses PLT files for caching project info. These are in _build/dev/, but they're only created
+          # when running dialyzer for the first time, and updated when the deps change.
+          key: ${{ runner.os }}-plts-${{ env.elixir_version }}-${{ env.otp_version }}-${{ hashFiles('**/mix.lock') }}
+          restore-keys: ${{ runner.os }}-plts-${{ env.elixir_version }}-${{ env.otp_version }}-
+
+      - name: Install Mix dependencies
+        run: mix deps.get
+
+      - name: Run dialyzer
+        run: mix dialyzer