feat: Translate frontend/src/i18n/en.json in is

80% of minimum 50% translated source file: 'frontend/src/i18n/en.json'
on 'is'.

Sync of partially translated files: 
untranslated content is included with an empty translation 
or source language content depending on file format

frontend/src/i18n/is.json

@@ -102,6 +102,7 @@
     "username": "Notendanafn",
     "usernameTaken": "Þetta norendanafn er þegar í notkun",
     "wrongCredentials": "Rangar notendaupplýsingar",
+    "passwordTooShort": "Password must be at least {min} characters",
     "logout_reasons": {
       "inactivity": "You have been logged out due to inactivity."
     }