settings: add search

- because tabs arent loaded at runtime, we have to have a separate index
- Less ideal, but functional enough for now

quickshell/Modules/Settings/WidgetsTab.qml

@@ -932,6 +932,7 @@ Item {
 
         Column {
             id: mainColumn
+            topPadding: 4
             width: Math.min(550, parent.width - Theme.spacingL * 2)
             anchors.horizontalCenter: parent.horizontalCenter
             spacing: Theme.spacingXL