[pitivi] mainwindow: Add Preferences keyboard shortcut

[Alexandru Băluț <alexbalut src gnome org>]

commit 1f30ee28ee7703bf484658194d7c46a226cc0693
Author: swayne <swayamjeet swain>
Date:   Tue Mar 26 21:12:17 2019 +0530

    mainwindow: Add Preferences keyboard shortcut
    
    Fixes #2287

 pitivi/mainwindow.py | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/pitivi/mainwindow.py b/pitivi/mainwindow.py
index 65ace502..6d5fdcaf 100644
--- a/pitivi/mainwindow.py
+++ b/pitivi/mainwindow.py
@@ -174,6 +174,8 @@ class MainWindow(Gtk.ApplicationWindow, Loggable):
         self.preferences_action = Gio.SimpleAction.new("preferences", None)
         self.preferences_action.connect("activate", self.__preferences_cb)
         self.add_action(self.preferences_action)
+        self.app.shortcuts.add("win.preferences", ["<Primary>comma"],
+                               _("Preferences"), group="app")
 
     @staticmethod
     def __user_manual_cb(unused_action, unused_param):