Add note to login and registration about alpha quality

briar-gtk/data/ui/login.ui

@@ -71,6 +71,23 @@
             <property name="left-attach">1</property>
           </packing>
         </child>
+        <child>
+          <object class="GtkLabel" id="alpha_label">
+            <property name="visible">True</property>
+            <property name="can_focus">False</property>
+            <property name="label" translatable="yes">Note: This is an alpha release of Briar GTK which may contain bugs</property>
+            <property name="xalign">0</property>
+            <property name="wrap">True</property>
+            <property name="wrap_mode">PANGO_WRAP_WORD_CHAR</property>
+            <style>
+              <class name="error-label"/>
+            </style>
+          </object>
+          <packing>
+            <property name="top-attach">3</property>
+            <property name="left-attach">1</property>
+          </packing>
+        </child>
       </object>
       <packing>
         <property name="name">password</property>

briar-gtk/data/ui/registration.ui

@@ -86,6 +86,18 @@
                 </style>
               </object>
             </child>
+            <child>
+              <object class="GtkLabel" id="alpha_label">
+                <property name="visible">True</property>
+                <property name="can_focus">False</property>
+                <property name="label" translatable="yes">Note: This is an alpha release of Briar GTK which may contain bugs</property>
+                <property name="wrap">True</property>
+                <property name="wrap_mode">PANGO_WRAP_WORD_CHAR</property>
+                <style>
+                  <class name="error-label"/>
+                </style>
+              </object>
+            </child>
           </object>
         </child>
       </object>