chg: [CI] add test pipeline

.github/workflows/test.yml

@@ -0,0 +1,25 @@
+name: "Test"
+on: ["push", "pull_request"]
+
+jobs:
+  test:
+    runs-on: ubuntu-20.04
+    name: OTP ${{ matrix.otp }} / Elixir ${{ matrix.elixir }}
+    strategy:
+      matrix:
+        otp: ["24.x"]
+        elixir: ["1.12.3", "1.13.3", "1.14.3", "1.15.3", "1.16.3"]
+    steps:
+      - uses: actions/checkout@v3
+
+      - uses: erlef/setup-beam@v1
+        name: Setup elixir
+        with:
+          otp-version: ${{matrix.otp}}
+          elixir-version: ${{matrix.elixir}}
+
+      - run: |
+          mix deps.get
+          mix compile --warnings-as-errors
+          mix format --check-formatted
+          mix test