Adding custom element polyfill (#177)

src/init-app.tsx

@@ -0,0 +1,24 @@
+import { h, render } from 'preact';
+import './lib/fix-pmc';
+import './style';
+import App from './components/App';
+
+// Find the outermost Element in our server-rendered HTML structure.
+let root = document.querySelector('#app') || undefined;
+
+// "attach" the client-side rendering to it, updating the DOM in-place instead of replacing:
+root = render(<App />, document.body, root);
+
+// In production, this entire condition is removed.
+if (process.env.NODE_ENV === 'development') {
+  // Enable support for React DevTools and some helpful console warnings:
+  require('preact/debug');
+
+  // When an update to any module is received, re-import the app and trigger a full re-render:
+  module.hot.accept('./components/App', () => {
+    // tslint:disable-next-line variable-name
+    import('./components/App').then(({ default: App }) => {
+      root = render(<App />, document.body, root);
+    });
+  });
+}