ci: add msrv check & update cargo.toml/readme rust-version to 1.60

.github/workflows/build.yml

@@ -7,7 +7,31 @@ on:
       - master
   pull_request: {}
 
+env:
+  RUST_MSRV: 1.60.0
+
 jobs:
+  msrv:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v3
+      - uses: actions/cache@v1
+        with:
+          path: |
+            ~/.cargo/bin
+            ~/.cargo/registry/index
+            ~/.cargo/registry/cache
+            ~/.cargo/git/db/
+            target
+          key: "${{ runner.os }}-cargo-build-msrv-${{ hashFiles('**/Cargo.lock') }}"
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: ${{ env.RUST_MSRV }}
+          override: true
+      - uses: actions-rs/cargo@v1
+        with:
+          command: check
   # typical build with various feature combinations
   build:
     name: Build