Adding custom element polyfill (#177)

package-lock.json

@@ -253,6 +253,12 @@
         "@xtuc/long": "4.2.1"
       }
     },
+    "@webcomponents/custom-elements": {
+      "version": "1.2.0",
+      "resolved": "https://registry.npmjs.org/@webcomponents/custom-elements/-/custom-elements-1.2.0.tgz",
+      "integrity": "sha512-KegC4y9/xlZNlEcKNtMmKXxNNMMLROzVntX55NfSgMhaXjwNf8EG8ypA2lt20ZQ/LoL0QuGxMZnf3kO5DdQjEQ==",
+      "dev": true
+    },
     "@xtuc/ieee754": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/@xtuc/ieee754/-/ieee754-1.2.0.tgz",

package.json

@@ -20,6 +20,7 @@
     "@types/node": "^9.6.23",
     "@types/pretty-bytes": "^5.1.0",
     "@types/webassembly-js-api": "0.0.1",
+    "@webcomponents/custom-elements": "^1.2.0",
     "babel-loader": "^7.1.5",
     "babel-plugin-jsx-pragmatic": "^1.0.2",
     "babel-plugin-syntax-dynamic-import": "^6.18.0",

src/index.ts

@@ -0,0 +1,9 @@
+declare module '@webcomponents/custom-elements';
+
+(async function () {
+  if (!('customElements' in self)) {
+    await import('@webcomponents/custom-elements');
+  }
+
+  require('./init-app.tsx');
+})();