add t/strings for username and password

src/components/NewPlaylist.vue

@@ -412,14 +412,14 @@ onMounted(async () => {
       <input
         class="textbox"
         type="text"
-        placeholder="username"
+        :placeholder="t('general.username')"
         autocomplete="username"
         @change="user.username = $event.target.value"
         required />
       <input
         class="textbox"
         type="password"
-        placeholder="password"
+        :placeholder="t('general.password')"
         autocomplete="password"
         @change="user.password = $event.target.value"
         required />

src/locales/de.json

@@ -85,8 +85,12 @@
         "void": "Keine Liedtexte"
     },
     "statusBar": {
-      "currentPlaylist": "Aktuelle Wiedergabeliste", 
-      "loop": "Schleife"
+        "currentPlaylist": "Aktuelle Wiedergabeliste", 
+        "loop": "Schleife"
+    },
+    "general": {
+        "username": "Benutzername",
+        "password": "Passwort"
     },
     "countries": {
         "AE": "Vereinigte Arabische Emirate",

src/locales/en.json

@@ -88,6 +88,10 @@
     "currentPlaylist": "Current Playlist", 
     "loop": "Loop"
   },
+  "general": {
+    "username": "username",
+    "password": "password"
+  },
   "countries": {
     "AE": "United Arab Emirates",
     "AR": "Argentina",