ci: exercise our tests and scripts on Windows too

This is more expensive, though, and not critical, so we don't want to
run these tests on every push in every PR, only on the actual push to
main.

Known limitation: "npx nx bundle web-component" only works in Git Bash on
Windows, not in cmd or PowerShell, so don't exercise it here, it'll just
fail every time.

Second limitation: we end up installing stuff twice, once for Cypress,
once for the rest of the processes. I'm not sure how to avoid that.
I leave it as future work to optimize this out.

.github/workflows/windows-tests.yml

@@ -0,0 +1,39 @@
+name: Run tests on Windows
+on:
+  push:
+    branches:
+      - main
+jobs:
+  tests-on-windows:
+    runs-on: windows-latest
+    timeout-minutes: 15
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+      - run: npm install --verbose
+      - name: Ng test for studio-web
+        run: |
+          npx nx build web-component
+          npx nx test:once studio-web
+
+      - name: Cypress run for web-component
+        uses: cypress-io/github-action@v6
+        with:
+          install: true # fails on Windows with install: false
+          start: |
+            npx nx serve web-component
+            npx nx serve-test-data web-component
+          wait-on: "http://localhost:3333/build/web-component.esm.js"
+          command: npx nx test:once web-component
+
+      - run: npx nx extract-i18n studio-web
+      - run: npx nx check-l10n studio-web
+      - run: npx nx build ngx-web-component
+      - run: npx nx build studio-web
+
+      # bundle only works in Git Bash on Windows, so don't exercise it here, we know it'll fail.
+      #- run: npx nx bundle web-component
+      #  shell: bash
+      #  continue-on-error: true