Check stated MSRV in CI

Author: djc

.github/workflows/rust.yml

@@ -25,6 +25,14 @@ jobs:
       run: cargo test --verbose --all-features --all
     - name: Build Examples
       run: cargo build --examples --all-features --all
+  msrv:
+    name: Minimum Supported Rust Version
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v3
+    - run: rustup toolchain add 1.63
+    - name: Build
+      run: cargo +1.63 check --lib --all-features
   clippy:
     name: Clippy
     runs-on: ubuntu-latest