Issue 5706 - Finish custom filter list dialog

locale/en-US/new-options.json

 {
   "options_page_title": {
     "description": "Options page title",
     "message": "Adblock Plus Options"
   },
   "options_page_title": {
     "description": "Page title in navigation sidebar",
     "message": "Settings"
   },
   "options_tab_general": {
@@ skipping 367 matching lines @@
     "message": "Adblock Plus is a registered ® trademark of eyeo GmbH."
   },
   "options_dialog_predefined_confirm": {
     "description": "Confirming to add a predefined subscription when asked in a dialog",
     "message": "Yes, use this filter list"
   },
   "options_dialog_predefined_title": {
     "description": "Dialog title for adding a predefined subscription",
     "message": "Do you really want to use this filter list?"
   },
-  "options_dialog_custom_title": {
-    "description": "Title of custom subscription modal dialog",
+  "options_dialog_import_title": {
+    "description": "Title of 'Add a filter list' dialog",
     "message": "Add a filter list"
   },
   "options_close": {
     "description": "Close modal button",
     "message": "close"
   },
-  "options_dialog_custom_subscription_title": {
-    "description": "Add custom subscription modal import hint message",
-    "message": "Filter list location"
+  "options_dialog_import_subscription_title": {
+    "description": "Input label in 'Add a filter list' dialog",
+    "message": "Filter list name"
   },
-  "options_dialog_custom_import": {
-    "description": "Button in add custom subscription modal dialog",
-    "message": "Add filter list"
+  "options_dialog_import_subscription_title_error": {
+    "description": "Error message of 'Filter list name' input in 'Add a filter list' dialog",
+    "message": "Please fill out the field"
+  },
+  "options_dialog_import_subscription_location": {
+    "description": "Input label in 'Add a filter list' dialog",
+    "message": "Filter list URL"
+  },
+  "options_dialog_import_subscription_location_error": {
+    "description": "Error message of 'Filter list URL' input in 'Add a filter list' dialog",
+    "message": "Enter a valid URL"
   },
   "options_dialog_edit_own_list": {
     "description": "Edit own filter list section name in custom subscription modal dialog",
     "message": "edit own filter list"
   },
    "options_dialog_language_title": {
     "description": "Title of lanugage modal dialog",
     "message": "Select a language"
   },
   "options_dialog_language_find": {
@@ skipping 80 matching lines @@
   },
   "options_language_ro": {
     "description": "Language name shown in add language modal dialog",
     "message": "Romanian"
   },
   "options_language_ru_uk": {
     "description": "Language name shown in add language modal dialog",
     "message": "Russian and Ukrainian"
   }
 }