[fractal/translators-comment] Translation: Add comment for number of unread

[Daniel Garcia Moreno <danigm src gnome org>]

commit 8001be223ba6e4d9e9d9afbc8dc07c4f09bbacfd
Author: Daniel García Moreno <dani danigm net>
Date:   Tue Apr 14 12:05:12 2020 +0200

    Translation: Add comment for number of unread
    
    Recently we add the number of rooms with unread messages in the
    application title but that string could be a bit confusing for
    translators. This patch adds a comment for translators, to clarify what
    is this placeholder for.
    
    https://gitlab.gnome.org/GNOME/fractal/-/merge_requests/551

 fractal-gtk/src/appop/mod.rs | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/fractal-gtk/src/appop/mod.rs b/fractal-gtk/src/appop/mod.rs
index 7c7e2a2d..18d7b32b 100644
--- a/fractal-gtk/src/appop/mod.rs
+++ b/fractal-gtk/src/appop/mod.rs
@@ -178,6 +178,8 @@ impl AppOp {
             if unread == 0 {
                 window.set_title(&i18n::i18n("Fractal"));
             } else {
+                // Translators: The placeholder is for the number of unread messages in the
+                // application
                 window.set_title(&i18n::i18n_f("Fractal [{}]", &[&unread.to_string()]));
             }
             self.unread_rooms = unread;