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/types/certificate.ts

@@ -0,0 +1,14 @@
+// Copyright (c) 2016-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+import {Certificate} from 'electron/common';
+
+export type ComparableCertificate = {
+    data: string;
+    issuerName: string;
+}
+
+export type CertificateModalData = {
+    url: string;
+    list: Certificate[];
+}