Add macOS CI

Author: jrmuizel

.github/workflows/rust.yml

@@ -8,7 +8,10 @@ env:
 jobs:
   build:
 
-    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        os: [ubuntu-latest, macos-latest]
+    runs-on: ${{ matrix.os }}
 
     steps:
     - uses: actions/checkout@v3