[css-pseudo-4] Fix image links

The links for each image referenced selectors, but these images are only contained in selectors 3. This change copies the images into css-pseudo-4 itself and fixes the links.

Author: csnardi

css-pseudo-4/Overview.bs

@@ -236,7 +236,7 @@ The ::first-letter pseudo-element</h3>
   in the ''::first-letter'' pseudo-element.
 
   <div class="figure">
-      <img alt="Quotes that precede the first letter should be included." src="https://www.w3.org/TR/selectors/first-letter2.png">
+      <img alt="Quotes that precede the first letter should be included." src="images/first-letter2.gif">
   </div>
 
   As explained in [[!CSS3TEXT]],
@@ -367,7 +367,7 @@ Styling the ''::first-letter'' Pseudo-element</h4>
     </pre>
 
     <div class="figure">
-        <img alt="Image illustrating the ::first-letter pseudo-element" src="https://www.w3.org/TR/selectors/initial-cap.png">
+        <img alt="Image illustrating the ::first-letter pseudo-element" src="images/initial-cap.png">
     </div>
   </div>
 
@@ -395,7 +395,7 @@ Styling the ''::first-letter'' Pseudo-element</h4>
 
     <div class="figure">
         <img alt="Image illustrating the combined effect of the ::first-letter
-   and ::first-line pseudo-elements" src="https://www.w3.org/TR/selectors/first-letter.png">
+   and ::first-line pseudo-elements" src="images/first-letter.gif">
     </div>
 
     The <a>fictional tag sequence</a> is: