Add Playwright test infrastructure for wxWidgets WASM port

- Add tests/ directory with Playwright e2e tests
- Add minimal wxWidgets WASM test application
- Add build script for test app (scripts/build-wasm-test.sh)
- Update wxWidgets submodule with WASM build fixes
- Update .gitignore for test artifacts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

tests/README.md

@@ -0,0 +1,43 @@
+# KiCad WASM Tests
+
+Playwright tests for verifying the wxWidgets WASM port.
+
+## Prerequisites
+
+- Node.js 18+
+- Emscripten SDK (for building)
+
+## Building the Test App
+
+```bash
+../scripts/build-wasm-test.sh
+```
+
+This builds `wasm-app/minimal_test.{html,js,wasm}`.
+
+## Running Tests
+
+```bash
+npm install
+npm test
+```
+
+## Viewing the App Directly
+
+Start a local server in the wasm-app directory:
+
+```bash
+cd wasm-app
+npx serve .
+```
+
+Then open http://localhost:3000/minimal_test.html in your browser.
+
+Alternative using Python:
+
+```bash
+cd wasm-app
+python3 -m http.server 8000
+```
+
+Then open http://localhost:8000/minimal_test.html