Fix svg thumbnail size

We need to use the contains attribute selector here, because
the url has a sha (for DDOS protection) and optionally other
parameters at the end of the url.

app/assets/stylesheets/alchemy/archive.scss

@@ -74,7 +74,7 @@
       background: $thumbnail-background;
     }
 
-    &[src$=".svg"]:not([src*="alchemy/missing-image"]) {
+    &[src*=".svg"]:not([src*="alchemy/missing-image"]) {
       width: var(--picture-width);
       max-height: var(--picture-height);
     }