clapper-app: Add "show pipeline" key shortcut to help overlay

Author: Rafostar

src/bin/clapper-app/ui/clapper-app-help-overlay.ui

@@ -26,6 +26,12 @@
                 <property name="accelerator">&lt;Ctrl&gt;question</property>
               </object>
             </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="title" translatable="yes">Show pipeline</property>
+                <property name="accelerator">&lt;Ctrl&gt;&lt;Shift&gt;p</property>
+              </object>
+            </child>
             <child>
               <object class="GtkShortcutsShortcut">
                 <property name="title" translatable="yes">Toggle fullscreen</property>