Add CI workflow.

.github/workflows/elixir.yml

@@ -0,0 +1,43 @@
+name: Elixir CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+permissions:
+  contents: read
+
+env:
+  ELIXIR_VERSION: "1.16.2"
+  ERLANG_VERSION: "26.2"
+
+jobs:
+  build:
+    name: Build and test
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: ./test/es6_maps_test
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Elixir
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: ${{ env.ELIXIR_VERSION }}
+          otp-version: ${{ env.ERLANG_VERSION }}
+
+      - name: Restore dependencies cache
+        uses: actions/cache@v4
+        with:
+          path: deps
+          key: ${{ runner.os }}-mix-${{ env.ELIXIR_VERSION }}-${{ env.ERLANG_VERSION }}-${{ hashFiles('**/mix.lock') }}
+
+      - name: Install dependencies
+        run: mix deps.get
+
+      - name: Run tests
+        run: mix test