implemented user login.

next: find a solution for routing

frontend/src/translations.svelte.js

@@ -7,12 +7,13 @@ export async function loadTranslation(lang){
     translations.values = await fetch(url).then(resp => resp.json());
 }
 
-export function t(key){
+export function t(key,...args){
     let set = translations.values;
-    var keys = key.split('.');
+    let keys = key.split('.');
     for (let key of keys){
         if (!set[key]) return keys[keys.length-1];
         set = set[key];
     }
+    for (var i in args) set = set.replace(`{${i}}`,args[i]);
     return set;
 }