feat(StatusFlatRoundButton): introduce `highlighted` color for secondary type

Closes #245

ui/StatusQ/sandbox/DemoApp.qml

@@ -450,6 +450,9 @@ Rectangle {
                     chatInfoButton.subTitle: "Community Chat"
                     chatInfoButton.icon.color: Theme.palette.miscColor6
                     chatInfoButton.type: StatusChatInfoButton.Type.CommunityChat
+
+                    searchButton.onClicked: searchButton.highlighted = !searchButton.highlighted
+                    membersButton.onClicked: membersButton.highlighted = !membersButton.highlighted
                 }
             }
         }

ui/StatusQ/src/StatusQ/Controls/StatusFlatRoundButton.qml

@@ -78,6 +78,15 @@ Rectangle {
                 return "transparent";
             }
         }
+
+        property color highlightedColor: {
+            switch(statusFlatRoundButton.type) {
+            case StatusFlatRoundButton.Type.Primary:
+                return Theme.palette.primaryColor3;
+            case StatusFlatRoundButton.Type.Secondary:
+                return Theme.palette.baseColor4;
+            }
+        }
     }
 
     implicitWidth: 44
@@ -86,8 +95,10 @@ Rectangle {
 
     color: {
         if (statusFlatRoundButton.enabled) {
-            return sensor.containsMouse || highlighted ? backgroundSettings.hoverColor
+            if (sensor.containsMouse) {
-                                        : backgroundSettings.color
+                return backgroundSettings.hoverColor
+            }
+            return highlighted ? backgroundSettings.highlightedColor : backgroundSettings.color
         } else {
             return backgroundSettings.disabledColor
         }