Format src files with Prettier (#215)

Formats files in `src` with [prettier for consistent code style](https://prettier.io/docs/en/why-prettier) and adds npm script

Related to https://github.com/webrecorder/replayweb.page/issues/201

src/electron-main.js

@@ -3,11 +3,10 @@
 import { ElectronReplayApp } from "./electron-replay-app";
 import path from "path";
 
-
 // ============================================================================
 const replayApp = new ElectronReplayApp({
   staticPath: path.join(__dirname, "../"),
-  profileName: "replaywebpage"
+  profileName: "replaywebpage",
 });
 
 replayApp.init(true);