title: GraphQL Where clause with boolean doesnt work (wpgraphql)
body: <p>I am using GraphQL in Wordpress as API with this plugin: <a href="https://docs.wpgraphql.com/getting-started/custom-fields-and-meta" rel="nofollow noreferrer">https://docs.wpgraphql.com/getting-started/custom-fields-and-meta</a> 
  I created custom field and I want to use where clause for boolean attribute but I get all record even those who dont match my where clause</p>
  
  <p>My query looks like this:</p>
  
  <pre><code>    query pagesInMenu {
   pages(where: { menu: true }) {
      edges {
        node {
          id
          menu
          title
        }
      }
    }
  }
  </code></pre>
  
  <p>And I get records where menu = false and menu = true ...
  It is custom field added via PHP code below:</p>
  
  <pre><code>function registerMenu($type) {
      register_graphql_field( $type, 'menu', [
          'type' =&gt; 'Boolean',
          'description' =&gt; __( 'Is in menu?', 'wp-graphql' ),
          'resolve' =&gt; function( $post ) {
              $menu = get_post_meta( $post-&gt;ID, 'menu', true );
              return ! empty( $menu ) ? ($menu == "true") : false;
          }
      ] );
  }
  
  add_action( 'graphql_register_types', registerMenu('Page') );
  add_action( 'graphql_register_types', registerMenu('RootQueryToPageConnectionWhereArgs') );
  </code></pre>