add GH actions workflow

.github/workflows/elixir.yml

@@ -0,0 +1,50 @@
+name: Elixir CI
+
+on:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+    merge_group:
+      types: [checks_requested]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+
+    name: Build and test
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+      - name: Set up Elixir v1.16 OTP26
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: "1.16.X" # Define the elixir version [required]
+          otp-version: "26.X" # Define the OTP version [required]
+      - name: Install dependencies
+        run: mix deps.get
+      - name: Run tests
+        run: mix test
+
+      - name: Set up Elixir v1.17 OTP26
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: "1.17.X" # Define the elixir version [required]
+          otp-version: "26.X" # Define the OTP version [required]
+      - name: Install dependencies
+        run: mix deps.get
+      - name: Run tests
+        run: mix test
+
+      - name: Set up Elixir v1.17 OTP27
+        uses: erlef/setup-beam@v1
+        with:
+          elixir-version: "1.17.X" # Define the elixir version [required]
+          otp-version: "27.X" # Define the OTP version [required]
+      - name: Install dependencies
+        run: mix deps.get
+      - name: Run tests
+        run: mix test