add streaming test

test/streaming.ts

+import WS from 'jest-websocket-mock';
+import Stream from '../src/streaming';
+
+describe('Streaming', () => {
+	test('success', async () => {
+		const server = new WS('wss://misskey.test/streaming');
+		const stream = new Stream('https://misskey.test', { token: 'TOKEN' });
+		const mainChannelReceived: any[] = [];
+		const main = stream.useSharedConnection('main');
+		main.on('foo', payload => {
+			mainChannelReceived.push(payload);
+		});
+		await server.connected;
+		const msg = JSON.parse(await server.nextMessage as string);
+		const mainChannelId = msg.body.id;
+		expect(msg.type).toEqual('connect');
+		expect(msg.body.channel).toEqual('main');
+		expect(mainChannelId != null).toEqual(true);
+
+		server.send(JSON.stringify({
+			type: 'channel',
+			body: {
+				id: mainChannelId,
+				type: 'foo',
+				body: {
+					bar: 'buzz'
+				}
+			}
+		}));
+
+		expect(mainChannelReceived[0]).toEqual({
+			bar: 'buzz'
+		});
+	});
+});