title: "OR" query in KeystoneJS Relationship Filters
body: <p>Currently, all I see examples for is:</p>
  
  <pre><code>{
     team: ':team'
  }
  </code></pre>
  
  <p>But I need to be able to filter by multiple values ($or query)</p>
  
  <p>Something like:</p>
  
  <pre><code>winner: {
     type: Types.Relationship,
     ref: 'Team',
     filters: [
        {
          _id: ':homeTeam'
        },
        {
          _id: ':awayTeam'
        }
     ]
  }
  </code></pre>
  
  <p>Is this possible?</p>