title: WKWebview stringByEvaluatingJavaScriptFromString equivalent?
body: <p><code>UIWebview</code> has (had?) an extremely useful function that enabled access to <code>javascript</code> variables from <code>Swift</code>.</p>
  
  <pre><code>func stringByEvaluatingJavaScriptFromString(_ script: String) -&gt; String?
  </code></pre>
  
  <p>Does <code>WKWebview</code> have an equivalent function or idiom enabling access to <code>javascript</code> variables from <code>Swift</code>?</p>