(feature) add tiny notifications example to bump travis

Author: f3rno

examples/ws2/notifications.js

@@ -0,0 +1,29 @@
+'use strict'
+
+process.env.DEBUG = 'bfx:examples:notifications'
+
+const debug = require('debug')('bfx:examples:notifications')
+const bfx = require('../bfx')
+const ws = bfx.ws(2)
+
+const run = async () => {
+  ws.on('error', (err) => {
+    debug('error: %s', err instanceof Error ? err.stack : err)
+  })
+
+  ws.onNotification({ type: '*' }, (n) => {
+    debug('recv notification: %j', n)
+  })
+
+  debug('connecting...')
+  await ws.open()
+  debug('connected')
+  await ws.auth()
+  debug('authenticated, listening for notifications')
+}
+
+try {
+  run()
+} catch (e) {
+  console.log(`error: ${e.stack}`)
+}