add action workflow

.github/workflows/elixir.yml

@@ -0,0 +1,35 @@
+name: Elixir CI
+
+on:
+  push:
+    branches: [ master ]
+  pull_request:
+    branches: [ master ]
+
+jobs:
+  build:
+
+    name: Build and test
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        elixir: [1.11, 1.10.4, 1.9, 1.8]
+        otp: [23.2, 22.3, 21.3]
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Set up Elixir
+      uses: erlef/setup-elixir@v1
+      with:
+          elixir-version: ${{ matrix.elixir }}
+          otp-version: ${{ matrix.otp }}
+    - name: Restore dependencies cache
+      uses: actions/cache@v2
+      with:
+        path: deps
+        key: ${{ runner.os }}-mix-${{ hashFiles('**/mix.lock') }}
+        restore-keys: ${{ runner.os }}-mix-
+    - name: Install dependencies
+      run: mix deps.get
+    - name: Run tests
+      run: mix test