Add footer to 'typing indicators' setting.

Signal/src/ViewControllers/AppSettings/PrivacySettingsTableViewController.m

@@ -108,7 +108,8 @@ static NSString *const kSealedSenderInfoURL = @"https://signal.org/blog/sealed-s
     OWSTableSection *typingIndicatorsSection = [OWSTableSection new];
     typingIndicatorsSection.headerTitle
         = NSLocalizedString(@"SETTINGS_TYPING_INDICATORS", @"Label for the 'typing indicators' setting.");
-    // TODO: Should we have a footer?
+    typingIndicatorsSection.footerTitle = NSLocalizedString(
+        @"SETTINGS_TYPING_INDICATORS_FOOTER", @"An explanation of the 'typing indicators' setting.");
     [typingIndicatorsSection addItem:[OWSTableItem switchItemWithText:NSLocalizedString(@"SETTINGS_TYPING_INDICATORS",
                                                                           @"Label for the 'typing indicators' setting.")
                                                                  isOn:[self.typingIndicators areTypingIndicatorsEnabled]

Signal/translations/en.lproj/Localizable.strings

@@ -2099,6 +2099,9 @@
 /* Label for the 'typing indicators' setting. */
 "SETTINGS_TYPING_INDICATORS" = "Typing Indicators";
 
+/* An explanation of the 'typing indicators' setting. */
+"SETTINGS_TYPING_INDICATORS_FOOTER" = "See and share when messages are being typed. This setting is optional and applies to all conversations.";
+
 /* Label for a link to more info about unidentified delivery. */
 "SETTINGS_UNIDENTIFIED_DELIVERY_LEARN_MORE" = "Learn More";