Fix: Center horizontal rules (---) in backlog pages

Author: Rishika12U

common-theme/layouts/partials/head.html

@@ -72,4 +72,6 @@
   <link rel="shortcut icon" href="{{ .Site.BaseURL }}favicon.ico" />
   <meta name="theme-color" content="#e3ddeef2" />
   <link rel="manifest" href="{{ .Site.BaseURL }}manifest.json" />
+  <link rel="stylesheet" href="/css/custom.css" /> 
+
 </head>

common-theme/static/css/custom.css

@@ -0,0 +1,5 @@
+hr {
+  margin-left: auto;
+  margin-right: auto;
+  width: 80%;
+}