Allow manual CI runs and restrict job permissions

.github/workflows/ci.yml

@@ -0,0 +1,33 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+  workflow_dispatch:
+
+jobs:
+  rust:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          components: rustfmt, clippy
+
+      - name: Cache cargo
+        uses: Swatinem/rust-cache@v2
+
+      - name: Rustfmt
+        run: cargo fmt --all -- --check
+
+      - name: Clippy
+        run: cargo clippy --all-targets --all-features -- -D warnings
+
+      - name: Tests
+        run: cargo test --all-targets --all-features