ci: Add a CI workflow to verify the minimum supported Rust version

.github/workflows/msrv.yaml

@@ -0,0 +1,21 @@
+name: Rust version
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+    types:
+      - opened
+      - reopened
+      - synchronize
+      - ready_for_review
+
+jobs:
+  msrv:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: taiki-e/install-action@cargo-hack
+    - run: cargo hack check --rust-version --workspace --all-targets --ignore-private