Add CI for windows and macos

Author: janbridley

.github/workflows/CI.yaml

@@ -15,6 +15,15 @@ jobs:
       matrix:
         python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"]
         runs-on: ["ubuntu-latest"]
+        include:
+          - os: "macos-latest"
+            python: "3.13"
+          - os: "windows-latest"
+            python: "3.13"
+          - os: "windows-latest"
+            python: "3.9"
+          - os: "macos-latest"
+            python: "3.9"
     # Pull in the test script from run_tests and distribute python from matrix versions
     uses: ./.github/workflows/run_tests.yaml
     with:
@@ -28,7 +37,7 @@ jobs:
       fail-fast: false # Legacy versions are much less stable - run tests independently
       matrix: # Code works on py3.6, but type annotations are broken
         python-version: ["3.7", "3.8"]
-        runs-on: ["ubuntu-20.04"]
+        runs-on: ["ubuntu-20.04", "windows-latest", "macos-14"]
     uses: ./.github/workflows/run_tests.yaml
     with:
       python-version: ${{ matrix.python-version }}