allow to skip 10s by pressing the arrow keys while scale is focused

fix #46

Author: vixalien

data/player.ui

@@ -34,6 +34,8 @@
                     <property name="upper">1</property>
                     <property name="lower">0</property>
                     <property name="value">0</property>
+                    <!-- Allow to skip 10 seconds by pressing the left and right keys -->
+                    <property name="step-increment">10000000</property>
                   </object>
                 </property>
               </object>