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

assets/romfs/i18n/en.json

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