Fix Windows uninstaller not removing files correctly

Multiple async tasks were not performed completely when running uninstaller.
So rearranged tasks with sequential order.
i.e. take care startup registry, finally call electron-squirrel-startup.

src/main.js

@@ -12,8 +12,7 @@ const {
 } = require('electron');
 const isDev = require('electron-is-dev');
 const installExtension = require('electron-devtools-installer');
-
-const AutoLaunch = require('auto-launch');
+const squirrelStartup = require('./main/squirrelStartup');
 
 process.on('uncaughtException', (error) => {
   console.error(error);
@@ -21,34 +20,8 @@ process.on('uncaughtException', (error) => {
 
 global.willAppQuit = false;
 
-if (process.platform === 'win32') {
-  var cmd = process.argv[1];
-  var appLauncher = new AutoLaunch({
-    name: 'Mattermost',
-    isHidden: true
-  });
-  if (cmd === '--squirrel-uninstall') {
-    // If we're uninstalling, make sure we also delete our auto launch registry key
-    appLauncher.isEnabled().then((enabled) => {
-      if (enabled) {
-        appLauncher.disable();
-      }
-    });
-  } else if (cmd === '--squirrel-install' || cmd === '--squirrel-updated') {
-    // If we're updating and already have an registry entry for auto launch, make sure to update the path
-    appLauncher.isEnabled().then((enabled) => {
-      if (enabled) {
-        return appLauncher.disable().then(() => {
-          return appLauncher.enable();
-        });
-      }
-      return true;
-    });
-  }
-}
-
 app.setAppUserModelId('com.squirrel.mattermost.Mattermost'); // Use explicit AppUserModelID
-if (require('electron-squirrel-startup')) {
+if (squirrelStartup()) {
   global.willAppQuit = true;
 }