Fixed link to manifest.json

Author: johnsgp

lib/source/layouts/core.erb

@@ -22,7 +22,7 @@
       <link rel="icon" sizes="any" href="<%= service_link %>assets/govuk/assets/images/favicon.svg" type="image/svg+xml">
       <link rel="mask-icon" href="<%= service_link %>assets/govuk/assets/images/govuk-icon-mask.svg" color="#0b0c0c">
       <link rel="apple-touch-icon" href="<%= service_link %>assets/govuk/assets/images/govuk-icon-180.png">
-      <link rel="manifest" href="/assets/govuk/assets/manifest.json">
+      <link rel="manifest" href="<%= service_link %>assets/govuk/assets/manifest.json">
     <% else %>
       <link rel="icon" sizes="48x48" href="/images/favicon.ico">
       <link rel="icon" sizes="any" href="/images/favicon.svg" type="image/svg+xml">