ci(github-workflows): add testing on MacOS and Windows

.github/workflows/dangerjs.yml

@@ -1,17 +1,19 @@
 ---
-name: DangerJS Pull Request linter
+name: 🎓 DangerJS Pull Request linter
 
 on:
-  pull_request_target:
-    types: [opened, edited, reopened, synchronize]
+  pull_request_target: {types: [opened, edited, reopened, synchronize]}
 
-permissions:
-  pull-requests: write
-  contents: write
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
 
 jobs:
   pull-request-style-linter:
     runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+      contents: write
     steps:
       - name: Check out PR head
         uses: actions/checkout@v4

.github/workflows/plugin-tests.yml

@@ -5,13 +5,18 @@ on:
   pull_request:
   push: {branches: master}
 
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref }}
+  cancel-in-progress: true
+
 jobs:
   plugin-tests:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
     permissions:
       contents: read
     strategy:
       matrix:
+        os: [ubuntu-latest, windows-latest, macos-latest]
         python-version: ['3.9', '3.10', '3.11', '3.12']
 
     steps:
@@ -24,14 +29,47 @@ jobs:
           python-version: ${{ matrix.python-version }}
           cache: pip
 
-      - name: Install dependencies
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Set up Python ${{ matrix.python-version }}
+        uses: actions/setup-python@v5
+        with:
+          python-version: ${{ matrix.python-version }}
+          cache: pip
+
+      - name: Create pip cache directory (Windows)
+        if: runner.os == 'Windows'
+        run: |
+          mkdir -p C:\Users\runneradmin\AppData\Local\pip\cache
+        shell: cmd
+
+      - name: (Linux/macOS) Install dependencies
+        if: runner.os != 'Windows'
         run: |
           python -m venv venv
           source venv/bin/activate
           pip install --require-virtualenv --upgrade pip
           pip install --require-virtualenv '.[test]'
+        shell: bash
 
-      - name: Run pytest, compare output with stored snapshots
-        run: |-
+      - name: (Linux/macOS) Run pytest, compare output with stored snapshots
+        if: runner.os != 'Windows'
+        run: |
           source venv/bin/activate
           pytest -s
+        shell: bash
+
+      - name: (Windows CMD) Install dependencies
+        if: runner.os == 'Windows'
+        run: |
+          python -m venv venv
+          venv\Scripts\python.exe -m pip install --require-virtualenv --upgrade pip
+          venv\Scripts\python.exe -m pip install --require-virtualenv '.[test]'
+        shell: cmd
+
+      - name: (Windows CMD) Run pytest, compare output with stored snapshots
+        if: runner.os == 'Windows'
+        run: |
+          venv\Scripts\python.exe -m pytest -s
+        shell: cmd