Fixed typo and added comments for user status messages

Reported at Transifex.

Fixed my questions at https://github.com/nextcloud/ios/commit/67f76d619b7bc044de61b42cb9789ce367f0f5c5 

Signed-off-by: rakekniven <mark.ziegler@rakekniven.de>

iOSClient/Supporting Files/en.lproj/Localizable.strings

@@ -155,11 +155,11 @@
 "_dnd_"                     = "Do not disturb";
 "_dnd_description_"         = "Mute all notifications";
 
-/* Please add context. What is invisible= */
+/* User status: Invisible= */
 "_invisible_"               = "Invisible";
 
-/* Please add context. What does apper mean? */
-"_invisible_description_"   = "Apper offline";
+/* User status: Appear offline */
+"_invisible_description_"   = "Appear offline";
 
 // App