Migrate app to TypeScript (#1637)

* Initial setup and migrated src/common

* WIP

* WIP

* WIP

* Main module basically finished

* Renderer process migrated

* Added CI step and some fixes

* Fixed remainder of issues and added proper ESLint config

* Fixed a couple issues

* Progress!

* Some more fixes

* Fixed a test

* Fix build step

* PR feedback

src/main/preload/mattermost.js

@@ -1,6 +1,6 @@
+// Copyright (c) 2015-2016 Yuya Ochiai
 // Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
-// Copyright (c) 2015-2016 Yuya Ochiai
 
 'use strict';