Restore extracting a MIME type for scripts

This regressed in 3d45584.

source

@@ -91597,6 +91597,10 @@ document.querySelector("button").addEventListener("click", bound);
    <li><p>Let <var>source text</var> be the result of <span data-x="UTF-8 decode">UTF-8
    decoding</span> <var>response</var>'s <span data-x="concept-response-body">body</span>.</p></li>
 
+   <li><p>Let <var>MIME type</var> be the result of <span data-x="extract a MIME type">extracting a
+   MIME type</span> from <var>response</var>'s <span data-x="concept-response-header-list">header
+   list</span>.</p></li>
+
    <li><p>Let <var>module script</var> be null.</p></li>
 
    <li><p>If <var>MIME type</var> is a <span>JavaScript MIME type</span> and <var>module type</var>
@@ -91605,10 +91609,10 @@ document.querySelector("button").addEventListener("click", bound);
    settings object</var>, <var>response</var>'s <span data-x="concept-response-url">url</span>, and
    <var>options</var>.</p></li>
 
-   <li><p>If the <span>MIME type essence</span> of <var>MIME type</var> is <code>text/css</code> and
-   <var>module type</var> is "<code data-x="">css</code>", then set <var>module script</var> to the
-   result of <span>creating a CSS module script</span> given <var>source text</var> and <var>module
-   map settings object</var>.</p></li>
+   <li><p>If the <span>MIME type essence</span> of <var>MIME type</var> is "<code>text/css</code>"
+   and <var>module type</var> is "<code data-x="">css</code>", then set <var>module script</var> to
+   the result of <span>creating a CSS module script</span> given <var>source text</var> and
+   <var>module map settings object</var>.</p></li>
 
    <li><p>If <var>MIME type essence</var> is a <span>JSON MIME type</span> and <var>module
    type</var> is "<code data-x="">json</code>", then set <var>module script</var> to the result of