ci: run build and test on all three platforms

Author: kermanx

.github/workflows/ci.yml

@@ -39,10 +39,12 @@ jobs:
         run: cargo dylint --all
 
   build:
-    name: Build
-    # TODO: Run CI on all three platforms.
-    runs-on: ubuntu-latest
+    name: Build (${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
     timeout-minutes: 50
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest, windows-latest]
     steps:
       - uses: actions/checkout@v4
       - name: Install Rust toolchain