Add clipboard error string

I pulled a Jay and forgot to stage something.

app/src/main/res/values/strings.xml

@@ -537,6 +537,7 @@
     </plurals>
     <string name="delete_downloads_for_manga">Delete downloaded chapters?</string>
     <string name="copied_to_clipboard">Copied to clipboard:\n%1$s</string>
+    <string name="clipboard_copy_error">Failed to copy to clipboard</string>
     <string name="source_not_installed">Source not installed: %1$s</string>
     <string name="snack_add_to_library">Add manga to library?</string>