Make it easier to spot reaction buttons

In dark themes it can be very hard to spot the reaction
buttons when using compact mode. 

Before:

![image](/uploads/f499f5fd16be353c5fef9b1a08e99522/image.png)

After:

![image](https://invent.kde.org/network/neochat/uploads/86e6cecc546d73481dff79debdcadc3f/image.png)

Also this uses the given colorscheme so it will work everywhere 😄

src/qml/ReactionDelegate.qml

@@ -53,7 +53,7 @@ Flow {
             background: Kirigami.ShadowedRectangle {
                 color: reactionDelegate.hasLocalUser ? Kirigami.Theme.positiveBackgroundColor : Kirigami.Theme.backgroundColor
                 Kirigami.Theme.inherit: false
-                Kirigami.Theme.colorSet: Kirigami.Theme.View
+                Kirigami.Theme.colorSet: Config.compactLayout ? Kirigami.Theme.Window : Kirigami.Theme.View
                 radius: height / 2
                 shadow {
                     size: Kirigami.Units.smallSpacing