Add dark mode

Issue: #1017

Author: dvogt23

themes/newsletter/templates/base.html

@@ -178,6 +178,45 @@
      blockquote p {
        white-space: pre-line;
      }
+
+    @media (prefers-color-scheme: dark) {
+      body {
+        background: black;
+        color: white;
+      }
+
+      p {
+        color: white;
+      }
+
+      td .row-header-01 {
+        color: white;
+      }
+
+      .ExternalClass {
+        color: white;
+      }
+
+      code {
+        color: #c7254e !important;
+        border: 1px solid #7f8c8d;
+        background-color: #ccd1d1;
+      }
+
+      h1,
+      h2 {
+        color: white;
+      }
+
+      table .container {
+        border-color: black;
+        border-top-color: #ccc;
+      }
+
+      blockquote {
+        background-color: #3c3c3c;
+      }
+    }
     </style>
   </head>