Enable dependabot update for Rust

Since Rust 1.64, Clippy respects `rust-version` field in Cargo.toml.
rust-lang/rust@b776fb8

.clippy.toml

@@ -1 +0,0 @@
-msrv = "1.47"

.github/dependabot.yml

@@ -0,0 +1,9 @@
+version: 2
+updates:
+  - package-ecosystem: cargo
+    directory: /
+    schedule:
+      interval: weekly
+    commit-message:
+      prefix: ''
+    labels: []

.github/workflows/ci.yml

@@ -6,11 +6,20 @@ on:
     branches:
       - master
   schedule:
-    - cron: '0 2 * * *'
+    - cron: '0 2 * * 0'
 
 env:
-  RUSTFLAGS: -D warnings
+  CARGO_INCREMENTAL: 0
+  CARGO_NET_RETRY: 10
+  CARGO_TERM_COLOR: always
   RUST_BACKTRACE: 1
+  RUSTFLAGS: -D warnings
+  RUSTDOCFLAGS: -D warnings
+  RUSTUP_MAX_RETRIES: 10
+
+defaults:
+  run:
+    shell: bash
 
 jobs:
   test:
@@ -31,16 +40,19 @@ jobs:
       - run: cargo test
 
   msrv:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
+        os: [ubuntu-latest, windows-latest]
         # When updating this, the reminder to update the minimum supported
-        # Rust version in Cargo.toml and .clippy.toml.
+        # Rust version in Cargo.toml.
         rust: ['1.47']
     steps:
       - uses: actions/checkout@v3
       - name: Install Rust
-        run: rustup update ${{ matrix.rust }} && rustup default ${{ matrix.rust }}
+        # --no-self-update is necessary because the windows environment cannot self-update rustup.exe.
+        run: rustup update ${{ matrix.rust }} --no-self-update && rustup default ${{ matrix.rust }}
       - run: cargo build
 
   clippy:
@@ -63,6 +75,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v3
-      - uses: actions-rs/audit-check@v1
+      # https://github.com/rustsec/audit-check/issues/2
+      - uses: rustsec/audit-check@master
         with:
           token: ${{ secrets.GITHUB_TOKEN }}