add simple message pane component

electrum/gui/qml/components/MessagePane.qml

@@ -0,0 +1,30 @@
+import QtQuick 2.6
+import QtQuick.Layouts 1.0
+import QtQuick.Controls 2.1
+import QtQuick.Controls.Material 2.0
+
+Rectangle {
+    id: item
+
+    property bool warning
+    property bool error
+    property string text
+
+    color: "transparent"
+    border.color: error ? "red" : warning ? "yellow" : Material.accentColor
+    border.width: 1
+    height: text.height + 2* 16
+    radius: 8
+
+    Text {
+        id: text
+        width: item.width - 2* 16
+        x: 16
+        y: 16
+
+        color: item.border.color
+        text: item.text
+        wrapMode: Text.Wrap
+    }
+
+}