Add a warning icon to the capabilities dialog

If the short source capabilities shows a warning icon, surely the long
form dialog should show the same information.

data/src-cap-dialog.ui

                           </packing>
                         </child>
                         <child>
-                          <object class="GtkLabel" id="power-label">
+                          <object class="GtkLabel" id="info-label">
                             <property name="visible">True</property>
                             <property name="can_focus">False</property>
                             <property name="halign">start</property>
                           </object>
                           <packing>
                             <property name="left_attach">1</property>
-                            <property name="top_attach">0</property>
+                            <property name="top_attach">1</property>
                           </packing>
                         </child>
                         <child>
-                          <object class="GtkLabel" id="info-label">
+                          <object class="GtkBox">
                             <property name="visible">True</property>
                             <property name="can_focus">False</property>
                             <property name="halign">start</property>
                             <property name="valign">start</property>
-                            <property name="label" translatable="yes">label</property>
+                            <property name="spacing">6</property>
+                            <child>
+                              <object class="GtkLabel" id="power-label">
+                                <property name="visible">True</property>
+                                <property name="can_focus">False</property>
+                                <property name="halign">start</property>
+                                <property name="valign">start</property>
+                                <property name="label" translatable="yes">label</property>
+                              </object>
+                              <packing>
+                                <property name="expand">False</property>
+                                <property name="fill">True</property>
+                                <property name="position">0</property>
+                              </packing>
+                            </child>
+                            <child>
+                              <object class="GtkImage" id="source-cap-warning">
+                                <property name="can_focus">False</property>
+                                <property name="tooltip_text" translatable="yes">Source violates the USB PD Power Rules</property>
+                                <property name="halign">start</property>
+                                <property name="icon_name">dialog-warning-symbolic</property>
+                              </object>
+                              <packing>
+                                <property name="expand">False</property>
+                                <property name="fill">True</property>
+                                <property name="position">1</property>
+                              </packing>
+                            </child>
                           </object>
                           <packing>
                             <property name="left_attach">1</property>
-                            <property name="top_attach">1</property>
+                            <property name="top_attach">0</property>
                           </packing>
                         </child>
                       </object>

pd-buddy-gtk.py

         # Populate PD Power
         d_power = dialog_builder.get_object("power-label")
         d_power.set_text("{:g} W".format(pdbuddy.calculate_pdp(caps)))
+        # Warning icon
+        cap_warning = dialog_builder.get_object("source-cap-warning")
+        cap_warning.set_visible(not pdbuddy.follows_power_rules(caps))
 
         # Populate Information
         d_info_header = dialog_builder.get_object("info-header")