Improve "Copy text" text and availability

TODO.md

@@ -1,6 +1,5 @@
 # TODO
 
-- show "copy selection" when right clicking on image
 - make it not select messages when closing context menu
 - long-press-drag to select multiple messages on touch
 - drag to select on non-touch

src/gui/Pages/Chat/Timeline/EventDelegate.qml

@@ -188,8 +188,15 @@ HColumnLayout {
 
         HMenuItem {
             icon.name: "copy-text"
-            text: qsTr("Copy text")
-            visible: ! copyLink.visible && ! copyMedia.visible
+            text:
+                eventList.selectedCount ?
+                qsTr("Copy selection") :
+
+                copyMedia.visible ?
+                qsTr("Copy filename") :
+
+                qsTr("Copy text")
+
             onTriggered: {
                 if (! eventList.selectedCount) {
                     Clipboard.text = JSON.parse(model.source).body