add banner requesting users to move to new domain

src/routes/+page.svelte

@@ -1,4 +1,7 @@
 <script lang="ts">
+    import { browser } from "$app/environment";
+    import { replaceState } from "$app/navigation";
+    import { page } from "$app/stores";
     import Leaderboards from "$lib/Leaderboards.svelte";
     import Meta from "$lib/Meta.svelte";
     import { onMount } from "svelte";
@@ -20,27 +23,27 @@
         let params = new URLSearchParams(window.location.search);
         params.set("channel", this.value);
         let url = window.location.pathname + "?" + String(params);
-        window.history.replaceState(null, "", url);
+        replaceState(url, $page.state);
     }
 
     function storeChannel(this: HTMLSelectElement) {
         localStorage.setItem("channel", this.value);
     }
 
     /** only those which have individual leadeboards */
-    const channels = [
-        "global",
-        "breadworms",
-        "psp1g",
-        "julialuxel",
-        "ovrht",
-        "omie",
-        "vaiastol"
-    ];
+    const channels = ["global", "breadworms", "psp1g", "julialuxel", "ovrht", "omie", "vaiastol"];
+
+    // should be removed in the future
+    const isOldDomain = browser ? window.location.hostname !== "gofish.lol" : false;
 </script>
 
 <Meta description="Leaderboards for gofish" title="gofish leaderboards" image="/favicon.png" />
 
+{#if isOldDomain}
+    <header class="p-4 text-3xl text-center bg-neutral-800">
+        Please use the new domain: <a href="https://gofish.lol/">https://gofish.lol/</a>
+    </header>
+{/if}
 <div class="ml-8 mr-8 lg:ml-32 lg:mr-32">
     <h1 class="mb-4 mt-8">gofish leaderboards! 🎣 🤩 🏆</h1>
     <span>channel: </span>