Increase the contrast for the copy icon in the search list. (dart-lang#8316)

Author: isoos

pkg/web_css/lib/src/_list.scss

@@ -193,7 +193,15 @@
  margin: 0px -30px 6px -30px;
  padding: 15px 30px;
 
+ .pkg-page-title-copy-icon {
+ opacity: 0.15;
+ }
+
  &:hover {
+ .pkg-page-title-copy-icon {
+ opacity: 0.25;
+ }
+
  background: var(--pub-neutral-hover-bgColor);
  }
  }