header: Notice about domain migration

_includes/header.html

@@ -0,0 +1 @@
+<header>The website of the Radicle project has moved from <i>radicle.xyz</i> to <i>radicle.dev</i>.</header>

_layouts/index.html

@@ -48,5 +48,10 @@
       }
     });
   </script>
+  <script>
+    if ((new URLSearchParams(window.location.search)).get("via") === "radicle.xyz") {
+      document.querySelector("header").style.visibility = "visible";
+    }
+  </script>
 </body>
 </html>

assets/css/page.css

@@ -258,9 +258,7 @@ body > main > header > h1 {
 
 body > header {
   position: relative;
-  color: var(--color-fg-low-contrast);
   border-bottom: 1px solid var(--color-border-hint);
-  font-weight: bold;
   white-space: nowrap;
   overflow: hidden;
   text-overflow: hidden;
@@ -269,6 +267,12 @@ body > header {
   height: 1.75rem;
   min-height: 1.5rem;
   line-height: 1.5rem;
+  text-align: center;
+  visibility: hidden;
+}
+
+body > header > i {
+  color: var(--color-pink);
 }
 
 body > footer {