Add dark mode styling

Author: Bellangelo

scripts/md2html/main.css

@@ -70,4 +70,59 @@ th code {
 
 a.bibref {
     text-decoration: underline;
+}
+
+@media (prefers-color-scheme: dark) {
+    body.darkmode {
+        --toclink-underline: #6a9000;
+        --toclink-visited-underline: #fff;
+    }
+
+    body.darkmode a,
+    body.darkmode .tocxref,
+    body.darkmode .u-url {
+        color: #6a9000;
+    }
+
+    body.darkmode code {
+        color: #e66c33;
+    }
+
+    body.darkmode:not(.toc-inline) #toc h2,
+    body.darkmode h1,
+    body.darkmode h2,
+    body.darkmode h3,
+    body.darkmode h4,
+    body.darkmode h5,
+    body.darkmode h6,
+    body.darkmode #title,
+    body.darkmode #subtitle,
+    body.darkmode .toc-inline,
+    body.darkmode .dt-published {
+        color: #7bb01c;
+    }
+
+    body.darkmode pre,
+    body.darkmode table tr:nth-child(2n),
+    body.darkmode table tr {
+        background-color: #1e1e1e !important;
+        color: #dcdcdc;
+    }
+
+    body.darkmode img {
+        background: transparent;
+    }
+
+    body.darkmode .logo img {
+        display: none;
+    }
+
+    body.darkmode .logo::before {
+        content: "";
+        display: inline-block;
+        height: 48px;
+        width: 175px;
+        background: url("https://raw.githubusercontent.com/OAI/OpenAPI-Style-Guide/refs/heads/main/graphics/bitmap/OpenAPI_Logo_Pantone.png") no-repeat center / contain;
+        vertical-align: middle;
+    }
 }