another try at fixing CI

Author: stevengj

.github/workflows/CI.yml

@@ -20,6 +20,16 @@ jobs:
           - ubuntu-latest
           - macOS-latest
           - windows-latest
+        arch:
+          - x64
+          - arm64
+        exclude:
+          - os: macOS-latest
+            arch: x64
+          - os: windows-latest
+            arch: arm64
+          - os: ubuntu-latest
+            arch: arm64
     steps:
       - uses: actions/checkout@v7
       - uses: julia-actions/setup-julia@v3