Message attached property

Create Message attached property to propagate parameters like room, timeline, index and maxContentWidth down to the message content avoiding lots of boilerplate

src/timeline/TextComponent.qml

@@ -35,11 +35,6 @@ TextEdit {
      */
     property bool spoilerRevealed: !hasSpoiler.test(display)
 
-    /**
-     * @brief The maximum width that the bubble's content can be.
-     */
-    property real maxContentWidth: -1
-
     /**
      * @brief Request a context menu be show for the message.
      */
@@ -47,7 +42,7 @@ TextEdit {
 
     Layout.fillWidth: true
     Layout.fillHeight: true
-    Layout.maximumWidth: root.maxContentWidth
+    Layout.maximumWidth: Message.maxContentWidth
 
     ListView.onReused: Qt.binding(() => !hasSpoiler.test(display))