Add our Salsa registration instruction link.

index.html

@@ -126,7 +126,7 @@ layout: default
       <li><a href="https://salsa.debian.org/reproducible-builds/diffoscope">Git repository</a></li>
       <li>
         <a href="https://salsa.debian.org/reproducible-builds/diffoscope/issues">Issues and feature requests</a>
-        <ul><li><a href="https://salsa.debian.org/reproducible-builds/diffoscope/issues/new">File a new issue!</a></li></ul>
+        <ul><li><a href="https://salsa.debian.org/reproducible-builds/diffoscope/issues/new">File a new issue!</a> (<a href="https://reproducible-builds.org/contribute/salsa/">registration instructions</a>)</li></ul>
       </li>
       <li><a href="https://lists.reproducible-builds.org/listinfo/diffoscope">Users and developers mailing-list</a></li>
       <li><code>#reproducible-builds</code> and/or <code>#debian-reproducible</code> on <a href="https://oftc.net/">OFTC</a></li>