add build workflow

.github/workflows/build.yml

@@ -0,0 +1,45 @@
+name: Build Game (Windows & Linux)
+
+on:
+  push:
+    branches: [ main, master ]
+  pull_request:
+
+jobs:
+  build:
+    name: Build and upload release artifacts
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Cache cargo registry and git index
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
+      - name: Install Rust (Ubuntu)
+        if: matrix.os == 'ubuntu-latest'
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Install Rust (Windows)
+        if: matrix.os == 'windows-latest'
+        run: choco install rust-ms -y
+
+      - name: Build (release)
+        run: cargo build --workspace --release
+
+      - name: Run tests
+        run: cargo test --workspace --verbose
+
+      - name: Upload release artifacts
+        uses: actions/upload-artifact@v4
+        with:
+          name: release-${{ matrix.os }}
+          path: target/release