Improves dialogs

* Fix some small spacing issues
* Add title

imports/NeoChat/Dialog/UserDetailDialog.qml

@@ -29,7 +29,7 @@ Kirigami.OverlaySheet {
 
     header: Kirigami.Heading {
         id: heading
-        text: i18n("@title:menu Account detail dialog", "Account detail")
+        text: i18nc("@title:menu Account detail dialog", "Account detail")
         elide: Text.ElideRight
         QQC2.ToolTip.visible: truncated && hovered
         QQC2.ToolTip.text: text

imports/NeoChat/Menu/Timeline/MessageDelegateContextMenu.qml

@@ -62,13 +62,16 @@ Loader {
             leftPadding: 0
             rightPadding: 0
 
+            header: Kirigami.Heading {
+                text: i18nc("@title:menu Message detail dialog", "Message detail")
+            }
+
             contentItem: ColumnLayout {
                 spacing: 0
                 RowLayout {
                     id: headerLayout
                     Layout.fillWidth: true
-                    Layout.leftMargin: Kirigami.Units.largeSpacing
-                    Layout.rightMargin: Kirigami.Units.largeSpacing
+                    Layout.margins: Kirigami.Units.largeSpacing
                     spacing: Kirigami.Units.largeSpacing
                     Kirigami.Avatar {
                         id: avatar