Put encoding of "emulatedLanguage" in a separate step.

Author: lutien

fetch.bs

@@ -4668,9 +4668,14 @@ the response. [[!HTTP-CACHING]]
    <li><p>Let <var>emulatedLanguage</var> be the <a>WebDriver BiDi emulated language</a> for
    <var>request</var>'s <a for=request>client</a>.
 
-   <li><p>If <var>emulatedLanguage</var> is non-null, then <a for="header list">append</a>
-   (`<code>Accept-Language</code>, <var>emulatedLanguage</var>, <a>isomorphic encoded</a>)
-   to <var>request</var>'s <a for=request>header list</a>.
+   <li><p>If <var>emulatedLanguage</var> is non-null:
+
+   <ol>
+    <li><p>Let <var>encodedEmulatedLanguage</var> be <var>emulatedLanguage</var>, <a>isomorphic encoded</a>.
+
+    <li><p><a for="header list">Append</a> (`<code>Accept-Language`</code>, <var>encodedEmulatedLanguage</var>)
+    to <var>request</var>'s <a for=request>header list</a>.
+   </ol>
   </ol>
 
  <li><p>If <var>request</var>'s <a for=request>header list</a>