Add examples for collect an HTTP quoted string

And remove a confusing note.

Closes #1068.

fetch.bs

@@ -307,9 +307,31 @@ and optionally an <var>extract-value flag</var>, run these steps:
  inclusive, within <var>input</var>.
 </ol>
 
-<p class="note no-backref">The <var>extract-value flag</var> argument makes this algorithm suitable
-for <a for="header list">getting, decoding, and splitting</a> and <a>parse a MIME type</a>, as well
-as other header value parsers that might need this.
+<div class=example id=example-http-quoted-string>
+ <table>
+  <tr>
+   <th>Input
+   <th>Output
+   <th>Output with the <var>extract-value flag</var> set
+   <th>Final <a>position variable</a> value
+  <tr>
+   <td>"<code><mark>"\</mark></code>"
+   <td>"<code>"\</code>"
+   <td>"<code>\</code>"
+   <td>2
+  <tr>
+   <td>"<code><mark>"Hello"</mark> World</code>"
+   <td>"<code>"Hello"</code>"
+   <td>"<code>Hello</code>"
+   <td>7
+  <tr>
+   <td>"<code><mark>"Hello \\ World\""</mark></code>"
+   <td>"<code>"Hello \\ World\""</code>"
+   <td>"<code>Hello \ World"</code>"
+   <td>18
+ </table>
+ <p class=tablenote><small>The <a>position variable</a> always starts at 0 in these examples.</small>
+</div>
 
 
 <h4 id=methods>Methods</h4>