Add help button to dialog

Change-Id: I2b4eab22da81379a94b21947872a4dc2e9214c5f
Reviewed-on: https://gerrit.libreoffice.org/11210Reviewed-by: Thomas Arnhold <thomas@arnhold.org>
Tested-by: Thomas Arnhold <thomas@arnhold.org>

extensions/uiconfig/spropctrlr/ui/datatypedialog.ui

@@ -46,6 +46,20 @@
                 <property name="position">1</property>
               </packing>
             </child>
+            <child>
+              <object class="GtkButton" id="help">
+                <property name="label">gtk-help</property>
+                <property name="visible">True</property>
+                <property name="can_focus">True</property>
+                <property name="receives_default">True</property>
+                <property name="use_stock">True</property>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">True</property>
+                <property name="position">2</property>
+              </packing>
+            </child>
           </object>
           <packing>
             <property name="expand">False</property>