search entry: add placeholder text

As per the design mockup, but "RingID" is changed to "number"
since we also support SIP.

Issue: #80819
Change-Id: I4efb66387150f7229157a0756ef3dbefd1bc4fc2
diff --git a/ui/ringmainwindow.ui b/ui/ringmainwindow.ui
index b1f802f..27aa1f1 100644
--- a/ui/ringmainwindow.ui
+++ b/ui/ringmainwindow.ui
@@ -149,6 +149,7 @@
                     <property name="xalign">0.5</property>
                     <property name="truncate-multiline">True</property>
                     <property name="max-length">256</property>
+                    <property name="placeholder-text" translatable="yes">Search contacts or enter number</property>
                   </object>
                   <packing>
                     <property name="expand">True</property>