add new strings and update ko.json, ja.json (#88)

assets/romfs/i18n/nl.json

@@ -30,6 +30,9 @@
   "Sd": "",
   "Image System memory": "",
   "Image microSD card": "",
+  "Slow": "",
+  "Normal": "",
+  "Fast": "",
   "Yes": "Ja",
   "No": "Nee",
   "Enabled": "Ingeschakeld",
@@ -87,6 +90,7 @@
   "Portuguese": "Português",
   "Russian": "Русский",
   "Swedish": "Svenska",
+  "Vietnamese": "Vietnamese",
   "Logging": "Loggen",
   "Replace hbmenu on exit": "Vervang hbmenu bij afsluiten",
   "Misc": "Diversen",
@@ -95,6 +99,7 @@
   "Install forwarders": "",
   "Install location": "",
   "Show install warning": "",
+  "Text scroll speed": "",
 
   "FileBrowser": "Bestandsbrowser",
   "%zd files": "%zd files",
@@ -233,6 +238,7 @@
   "Update avaliable: ": "",
   "Download update: ": "",
   "Updated to ": "",
+  "Press OK to restart Sphaira": "",
   "Restart Sphaira?": "",
   "Failed to download update": "",
   "Restore hbmenu?": "",