move index.js to app.jsx and add new index.js shim

Note that the code inside app.jsx is exactly what used to be in index.js
so this change causes no functional difference and just represents
preparation for upcoming changes. It simplifies at least two upcoming
changes: one wants the app code to be in a different file and the other
is simplified by JSX syntax.

Author: Christopher Willis-Ford

src/renderer/app.jsx

@@ -0,0 +1,49 @@
+import {ipcRenderer, shell} from 'electron';
+import React from 'react';
+import ReactDOM from 'react-dom';
+import GUI, {AppStateHOC} from 'scratch-gui';
+
+import ElectronStorageHelper from '../common/ElectronStorageHelper';
+
+import styles from './app.css';
+
+const defaultProjectId = 0;
+
+// override window.open so that it uses the OS's default browser, not an electron browser
+window.open = function (url, target) {
+    if (target === '_blank') {
+        shell.openExternal(url);
+    }
+};
+// Register "base" page view
+// analytics.pageview('/');
+
+const appTarget = document.getElementById('app');
+appTarget.className = styles.app || 'app'; // TODO
+document.body.appendChild(appTarget);
+
+GUI.setAppElement(appTarget);
+const WrappedGui = AppStateHOC(GUI);
+
+const onStorageInit = storageInstance => {
+    storageInstance.addHelper(new ElectronStorageHelper(storageInstance));
+    // storageInstance.addOfficialScratchWebStores(); // TODO: do we want this?
+};
+
+const guiProps = {
+    onStorageInit,
+    isScratchDesktop: true,
+    projectId: defaultProjectId,
+    showTelemetryModal: (typeof ipcRenderer.sendSync('getTelemetryDidOptIn')) !== 'boolean',
+    onTelemetryModalOptIn: () => {
+        ipcRenderer.send('setTelemetryDidOptIn', true);
+    },
+    onTelemetryModalOptOut: () => {
+        ipcRenderer.send('setTelemetryDidOptIn', false);
+    },
+    onProjectTelemetryEvent: (event, metadata) => {
+        ipcRenderer.send(event, metadata);
+    }
+};
+const wrappedGui = React.createElement(WrappedGui, guiProps);
+ReactDOM.render(wrappedGui, appTarget);

src/renderer/index.js

@@ -1,49 +1 @@
-import {ipcRenderer, shell} from 'electron';
-import React from 'react';
-import ReactDOM from 'react-dom';
-import GUI, {AppStateHOC} from 'scratch-gui';
-
-import ElectronStorageHelper from '../common/ElectronStorageHelper';
-
-import styles from './app.css';
-
-const defaultProjectId = 0;
-
-// override window.open so that it uses the OS's default browser, not an electron browser
-window.open = function (url, target) {
-    if (target === '_blank') {
-        shell.openExternal(url);
-    }
-};
-// Register "base" page view
-// analytics.pageview('/');
-
-const appTarget = document.getElementById('app');
-appTarget.className = styles.app || 'app'; // TODO
-document.body.appendChild(appTarget);
-
-GUI.setAppElement(appTarget);
-const WrappedGui = AppStateHOC(GUI);
-
-const onStorageInit = storageInstance => {
-    storageInstance.addHelper(new ElectronStorageHelper(storageInstance));
-    // storageInstance.addOfficialScratchWebStores(); // TODO: do we want this?
-};
-
-const guiProps = {
-    onStorageInit,
-    isScratchDesktop: true,
-    projectId: defaultProjectId,
-    showTelemetryModal: (typeof ipcRenderer.sendSync('getTelemetryDidOptIn')) !== 'boolean',
-    onTelemetryModalOptIn: () => {
-        ipcRenderer.send('setTelemetryDidOptIn', true);
-    },
-    onTelemetryModalOptOut: () => {
-        ipcRenderer.send('setTelemetryDidOptIn', false);
-    },
-    onProjectTelemetryEvent: (event, metadata) => {
-        ipcRenderer.send(event, metadata);
-    }
-};
-const wrappedGui = React.createElement(WrappedGui, guiProps);
-ReactDOM.render(wrappedGui, appTarget);
+import './app.jsx';