title: In GraphQL for WordPress, how to get page by title
body: <p>Is it possible to get a page by it's title instead of it's ID?  I am using a custom page type but title field is by default so no change there.  Here is what I got:</p>
  <pre><code>query GET_PAGE($title: String){
    gastbyPage(where: {title:$title}) {
        id
        title
    }
  }
  </code></pre>
  <p>Here is the error I get:</p>
  <pre><code>&quot;Unknown argument \&quot;where\&quot; on field \&quot;gastbyPage\&quot; of type \&quot;RootQuery\&quot;.&quot;
  </code></pre>
  <p>Here is a working query if I am using ID:</p>
  <pre><code>query GET_PAGE($id: ID!){
    gastbyPage(id:$id) {
        id
        title
    }
  }
  </code></pre>
  <p>This is the expected result, and what I get if I query by ID:</p>
  <pre><code>{
      &quot;data&quot;: {
          &quot;gastbyPage&quot;: {
              &quot;id&quot;: &quot;cG9zdDoyMA==&quot;,
              &quot;title&quot;: &quot;My Title&quot;
          }
      },
      &quot;extensions&quot;: {
          &quot;debug&quot;: []
      }
  }
  </code></pre>