[kcms/users]: Improve appearance of avatar selection

BUG: 430016
FIXED-IN: 5.21

kcms/users/package/contents/ui/UserDetailsPage.qml

@@ -317,15 +317,25 @@ SimpleKCM {
 
                             Image {
                                 id: imgDelegate
+                                visible: false
                                 smooth: true
                                 mipmap: true
-
+                                sourceSize.width: Kirigami.Units.gridUnit * 5
-                                anchors.fill: parent
+                                sourceSize.height: Kirigami.Units.gridUnit * 5
                                 source: modelData
 
                                 Accessible.ignored: true
                             }
 
+                            Kirigami.ShadowedTexture {
+                                radius: width / 2
+                                anchors.centerIn: parent
+                                width: Kirigami.Units.gridUnit * 5
+                                height: Kirigami.Units.gridUnit * 5
+
+                                source: imgDelegate
+                            }
+
                             onClicked: {
                                 picturesSheet.close()
                                 usersDetailPage.oldImage = usersDetailPage.user.face