Fix broken thumbnail URLs in gallery example (#83)

Resolves issue introduced in #59 by caa89b7

examples/gallery/index.md

@@ -6,8 +6,8 @@ footnote = "Generated with Anchovy!"
 # Photo Gallery
 
 <div class="gallery">
-    <a href="static/images/home-sweet-home-cdk.webp"><img src="static/images/home-sweet-home-cdk.thumb.png" alt="A Vintage Automobile"></a>
-    <a href="static/images/nice-wheels-cdk.webp"><img src="static/images/nice-wheels-cdk.thumb.png" alt="A Old Wood-Sided House"></a>
-    <a href="static/images/stormy-cdk.webp"><img src="static/images/stormy-cdk.thumb.png" alt="A Boardwalk and Damaged Pines During a Storm"></a>
-    <a href="static/images/quayside-newcastle.webp"><img src="static/images/quayside-newcastle.thumb.png" alt="A Quay in Newcastle, England"></a>
+    <a href="static/images/home-sweet-home-cdk.webp"><img src="static/images/home-sweet-home-cdk.thumb.webp" alt="A Vintage Automobile"></a>
+    <a href="static/images/nice-wheels-cdk.webp"><img src="static/images/nice-wheels-cdk.thumb.webp" alt="A Old Wood-Sided House"></a>
+    <a href="static/images/stormy-cdk.webp"><img src="static/images/stormy-cdk.thumb.webp" alt="A Boardwalk and Damaged Pines During a Storm"></a>
+    <a href="static/images/quayside-newcastle.webp"><img src="static/images/quayside-newcastle.thumb.webp" alt="A Quay in Newcastle, England"></a>
 </div>