Add CI.

.github/workflows/rust.yml

@@ -0,0 +1,29 @@
+name: Rust
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+  merge_group:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  build-nightly:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+
+      - name: Check fmt
+        run: cargo fmt -- --check
+      - name: Build
+        run: ./ci.sh