add error page

Author: frodesundby

src/routes/+error.svelte

@@ -0,0 +1,11 @@
+<img class="centered" src="logo404.png" alt=""/>
+<style>
+    .centered {
+    text-align: center;
+    position: absolute;
+    top: 20%;
+    left: 50%;
+    transform: translate(-50%, -50%);
+    width: 300px;
+}
+</style>