refactor: more translation strings

src/assets/i18n/de.json

@@ -1,5 +1,6 @@
 {
   "CLOSE": "Schließen",
+  "PLAYLISTS": "Playlisten",
   "CHANNELS": {
     "ALL_CHANNELS": "Alle Sender",
     "FAVORITES": "Favoriten",

src/assets/i18n/en.json

@@ -1,5 +1,6 @@
 {
   "CLOSE": "Close",
+  "PLAYLISTS": "Playlists",
   "HOME": {
     "TITLE": "IPTVnator",
     "SUBTITLE": "Please select a playlist from the list or add a new playlist",