Add GitHub Actions CI for Linux, macOS, and Windows builds

.github/workflows/ci.yml

@@ -0,0 +1,45 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: Build (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
+        rust: [stable]
+        include:
+          - os: ubuntu-latest
+            rust: beta
+          - os: macos-latest
+            rust: beta
+          - os: windows-latest
+            rust: beta
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@master
+        with:
+          toolchain: ${{ matrix.rust }}
+          components: rustfmt
+
+      - name: Check formatting
+        run: cargo fmt -- --check
+
+      - name: Build
+        run: cargo build --verbose
+
+      - name: Run tests
+        run: cargo test --verbose

Cargo.toml

@@ -17,7 +17,9 @@ jwalk = "0.5"
 structopt = "0.3"
 filesize = "0.2.0"
 unicode-width = "0.1.7"
+[target.'cfg(not(target_os = "windows"))'.dependencies]
 nix = "0.17.0"
+
 [target.'cfg(windows)'.dependencies]
 winapi = { version = "0.3", features = ["securitybaseapi","debugapi"] }