title: Vue.set() on nested array properties
body: <p>i've been trying to trigger Vue DOM updates by updating an array the old way and it obviously wont do it because of the ceveats on Vue detecting object/array changes. I dont know how to access my nested array properties by using Vue.set. Normally i would access and assign my property like this (by the way this is a state in Vuex):</p>
  
  <pre><code>state.timelines[0].events[0].item.info = payload.info
  </code></pre>
  
  <p>I dont know how to access and assign that property with .set, i've tried a few combinations but they failed to work. Thanks.</p>