Webxrdevice (#2000)

* crates/web-sys/webidls/enabled/WebXRDevice.webidl

* Add WebXR Web IDL.

* Add WebXr example.

* Workaround in WebXR for FrozenArray and XRWebGLLayer constructor.

* Remove commented code.

* Attempt to improve WebXr example.

* Add WebXr as unstable WebIDL.

* Fixes for XRWebGLLayer.

* Tidy up WebXR example code.

* Update WebXr example docs.

Co-authored-by: Kev Kirkland <kev.kirkland@elucidata.co.uk>

examples/webxr/webpack.config.js

@@ -0,0 +1,27 @@
+const path = require('path');
+const HtmlWebpackPlugin = require('html-webpack-plugin');
+const webpack = require('webpack');
+const WasmPackPlugin = require("@wasm-tool/wasm-pack-plugin");
+
+module.exports = {
+    entry: './index.js',
+    output: {
+        path: path.resolve(__dirname, 'dist'),
+        filename: 'index.js',
+    },
+    plugins: [
+        new HtmlWebpackPlugin({
+            template: 'index.html'
+        }),
+      new WasmPackPlugin({
+          crateDirectory: path.resolve(__dirname, ".")
+      }),
+        // Have this example work in Edge which doesn't ship `TextEncoder` or
+        // `TextDecoder` at this time.
+        new webpack.ProvidePlugin({
+          TextDecoder: ['text-encoding', 'TextDecoder'],
+          TextEncoder: ['text-encoding', 'TextEncoder']
+        })
+    ],
+    mode: 'development'
+};