feat: add GitHub Actions workflow for testing and formatting checks

Author: kasvith

.github/workflows/test.yml

@@ -0,0 +1,50 @@
+name: Test
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+    branches: [ main, master ]
+
+jobs:
+  test:
+    name: Test
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        elixir: ['1.18']
+        otp: ['27']
+
+    steps:
+    - uses: actions/checkout@v4
+    
+    - name: Set up Elixir
+      uses: erlef/setup-beam@v1
+      with:
+        elixir-version: ${{ matrix.elixir }}
+        otp-version: ${{ matrix.otp }}
+        
+    - name: Set up Rust
+      uses: actions-rs/toolchain@v1
+      with:
+        toolchain: stable
+        override: true
+        
+    - name: Restore dependencies cache
+      uses: actions/cache@v4
+      with:
+        path: deps
+        key: ${{ runner.os }}-mix-${{ hashFiles('**/mix.lock') }}
+        restore-keys: ${{ runner.os }}-mix-
+        
+    - name: Install dependencies
+      run: mix deps.get
+      
+    - name: Compile
+      run: mix compile --warnings-as-errors
+      
+    - name: Run tests
+      run: mix test
+      
+    - name: Check formatting
+      run: mix format --check-formatted