feat: support importing emails from .zip archives

locales/lv/common.json

@@ -270,7 +270,7 @@
     "print": "Drukāt",
     "view_source": "Skatīt avota kodu",
     "export_email": "Eksportēt kā .eml",
-    "import_email": "Importēt .eml",
+    "import_email": "Importēt .eml vai .zip",
     "keyboard_shortcuts": "Īsinājumtaustiņi (?)",
     "email_source": "Vēstules avota kods",
     "draft_banner": "Šī vēstule ir melnraksts",
@@ -1794,7 +1794,7 @@
     "new_subfolder": "Jauna apakšmape...",
     "new_folder": "Jauna mape...",
     "rename": "Pārsaukt...",
-    "import_email": "Importēt .eml...",
+    "import_email": "Importēt .eml vai .zip...",
     "empty_folder": "Iztukšot mapi",
     "empty_folder_generic": "Iztukšot mapi",
     "delete_folder": "Dzēst mapi",