Implement improvements: rayon parallelism, safer CLI, output file option, tests, CI workflow, tuned release profile

.github/workflows/ci.yml

@@ -0,0 +1,27 @@
+name: CI
+
+on:
+  push:
+    branches: [ "**" ]
+  pull_request:
+    branches: [ "**" ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust toolchain
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          override: true
+      - name: Run cargo fmt check
+        run: cargo fmt -- --check
+      - name: Run clippy
+        run: cargo clippy --all-targets --all-features -- -D warnings
+      - name: Run tests
+        run: cargo test --verbose
+      - name: Build release
+        run: cargo build --release --verbose