build: add scheduled GH workflow for nightly

.github/workflows/ci_nightly.yaml

@@ -0,0 +1,44 @@
+name: ci-nightly
+
+on:
+  schedule:
+    - cron: 0 6,18 * * *
+
+jobs:
+  ci:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out
+        uses: actions/checkout@v3
+
+      - name: Install Rust toolchain
+        run: |
+          rustup update
+          rustup toolchain install nightly --profile minimal
+          rustup component add rustfmt --toolchain nightly
+          rustup component add clippy --toolchain nightly
+
+      - name: Install just
+        uses: taiki-e/install-action@v2
+        with:
+          tool: just
+
+      - name: Install protoc
+        uses: arduino/setup-protoc@v2
+        with:
+          repo-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up Rust cache
+        uses: Swatinem/rust-cache@v2
+
+      - name: Check code format
+        run: just fmt_check
+
+      - name: Run linter
+        run: just lint
+
+      - name: Run tests
+        run: just test
+
+      - name: Run doc
+        run: just doc