feat(navbar): add signup placeholder function

replacing a button with no action with a placeholder function that
launches an alert

src/lib/components/Navbar.svelte

@@ -6,6 +6,7 @@
   export let logged_in_user: User | undefined = undefined;
   export let nip07_plugin: boolean | undefined = undefined;
   export let login_function: Function = () => {};
+  export let singup_function: Function = () => {};
 </script>
 
 <div class="bg-base-400">
@@ -32,7 +33,12 @@
             class="btn normal-case btn-sm btn-ghost">Login</button
           >
         {:else}
-          <div class="btn normal-case btn-sm btn-ghost">Sign up</div>
+          <button
+            on:click={() => {
+              singup_function();
+            }}
+            class="btn normal-case btn-sm btn-ghost">Sign up</button
+          >
         {/if}
       </div>
     </div>

src/lib/wrappers/Navbar.svelte

@@ -8,6 +8,12 @@
     import { onMount } from "svelte";
     import Navbar from "$lib/components/Navbar.svelte";
 
+    let singup_function: Function = () => {
+        alert(
+            "a NIP-07 browser extension is required. currently no signup page",
+        );
+    };
+
     onMount(checkForNip07Plugin);
 </script>
 
@@ -15,4 +21,5 @@
     logged_in_user={$logged_in_user}
     nip07_plugin={$nip07_plugin}
     login_function={login}
+    {singup_function}
 />