title: Using vuex with typescript
body: <p>I am trying to use Typescript with a Vue project in which I use vuex for the data state management. In the <a href="https://vuex.vuejs.org/en/" rel="nofollow noreferrer">Vuex site</a> it says:</p>
  
  <blockquote>
    <p>Note: for TypeScript users, vuex@3.0+ requires vue@2.5+, and vice versa.</p>
  </blockquote>
  
  <p>However, there is no usage hint or specification around the site.</p>
  
  <p>So, assuming we already have Vuex@3.0+ and Vue@2.5+, what is the thing to be done for Typescript implementation in the store member(s)? Should we have a separate file for types (i.e. <code>types.ts</code>) and store the data types as Typescript interfaces/classes there etc.?</p>
  
  <p>P.S: The seamless usage of Typescript also with Vuex's <a href="https://vuex.vuejs.org/en/modules.html#Namespacing" rel="nofollow noreferrer">namespaced</a> property would be perfectly nice.</p>