Fix 404 issues link (#503)

Signed-off-by: Nicolas MASSART <nicolas.massart@consensys.net>

custom_theme/404.html

@@ -18,7 +18,7 @@
 </p>
 <p style="text-align: center">
   If you think we made a mistake and deleted a page that should be here, then please tell us on
-  <a href="{{config.extra.support.chat}}">{{config.site_name}} chat channel</a> or <a href="{{config.extra.support.issues}}">create an issue</a>.
+  <a href="{{config.extra.support.chat}}">{{config.site_name}} chat channel</a> or <a href="{{config.extra.support.doc_issues}}">create an issue on the doc repository</a>.
 </p>
 
 {% endblock %}

mkdocs.yml

@@ -30,6 +30,7 @@ extra:
     email: besu@lists.hyperledger.org
     website: https://www.hyperledger.org/projects/besu
     issues: https://github.com/hyperledger/besu/issues
+    doc_issues: https://github.com/hyperledger/besu-docs/issues/new/choose
   google:
     site_verification: 'sGzYdFR_AYDRtsC-SNxMRwjellnfTgs5ZA0q7GIM5j0'
     tag_manager: 'GTM-TS3WLJM'