ci(Testing): add TypeScript test job (#4002)

* ci(Testing): add TypeScript job

* chore: add eol before eof

typings/index.ts

@@ -0,0 +1,28 @@
+/// <reference path="index.d.ts" />
+
+import { Client } from 'discord.js';
+
+const client: Client = new Client();
+
+client.on('ready', () => {
+  console.log(`Client is logged in as ${client.user!.tag} and ready!`);
+});
+
+client.on('guildCreate', g => {
+  const channel = g.channels.cache.random();
+  if (!channel) return;
+
+  channel.setName('foo').then(updatedChannel => {
+    console.log(`New channel name: ${updatedChannel.name}`);
+  });
+});
+
+client.on('messageReactionRemoveAll', async message => {
+  console.log(`messageReactionRemoveAll - id: ${message.id} (${message.id.length})`);
+
+  if (message.partial) message = await message.fetch();
+
+  console.log(`messageReactionRemoveAll - content: ${message.content}`);
+});
+
+client.login('absolutely-valid-token');