Disallow import() in worklets

Closes w3c/css-houdini-drafts#506.

source

@@ -91365,6 +91365,21 @@ import "https://example.com/foo/../module2.mjs";</code></pre>
   <ol>
    <li><p>Let <var>settings object</var> be the <span>current settings object</span>.</p></li>
 
+   <li>
+    <p>If <var>settings object</var>'s <span data-x="concept-settings-object-global">global
+    object</span> implements <code>WorkletGlobalScope</code>, then:</p>
+
+    <ol>
+     <li><p>Let <var>completion</var> be Completion { [[Type]]: throw, [[Value]]: a new
+     <code>TypeError</code>, [[Target]]: empty }.</p></li>
+
+     <li><p>Perform <span>FinishDynamicImport</span>(<var>referencingScriptOrModule</var>,
+     <var>specifier</var>, <var>promiseCapability</var>, <var>completion</var>).</p></li>
+
+     <li><p>Return.</p></li>
+    </ol>
+   </li>
+
    <li><p>Let <var>base URL</var> be <var>settings object</var>'s <span>API base
    URL</span>.</p></li>