use onMount event instead of DOMready

ref #56

src/components/Footer.svelte

@@ -1,7 +1,8 @@
 <script>
+  import { onMount } from "svelte";
   import { _ } from "svelte-i18n";
   $: releaseinfo = "";
-  document.addEventListener("DOMContentLoaded", (event) => {
+  onMount(() => {
     releaseinfo = document
       .getElementById("buildinfo")
       .textContent.replace("RELEASE_INFO-", "")